1 03 748
697 451 1938
HEATING VENTILATING
AIR CONDITIONING
GUIDE 1938
TEXT .AND ILLUSTRATIONS -ARE KXIJLLY PRO-
TECTED SY COPYRIGHT .A.ND NOTHING
AF*I>EARS M:AY BE REJ»RJNTED EITHER
OR Z>T P-ART \VITHOtTT SPEGJjVL PER1V4TIS SION .
HEATING VENTILATING
AIR CONDITIONING
GUIDE
1938
AN INSTRUMENT OF SERVICE PREPARED FOR THE PROFESSION — CONTAINING A
Technical Data Section
OF REFERENCE MATERIAL ON THE DESIGN AND SPECIFICATION OF HEATING,
VENTILATING AND AIR CONDITIONING SYSTEMS — BASED ON THE TRANS-
ACTIONS— THE INVESTIGATIONS OF THE RESEARCH LABORATORY AND CO-
OPERATING INSTITUTIONS — AND THE PRACTICE OF THE MEMBERS AND
FRIENDS OF THE SOCIETY
TOGETHER WITH A
Manufacturers9 Catalog Data Section
CONTAINING ESSENTIAL AND RELIABLE INFORMATION CONCERNING
MODERN EQUIPMENT
ALSO
The Roll of Membership of the Society
WITH
Complete Indexes
TO TECHNICAL AND CATALOG DATA SECTIONS
Vol. 16
$5.00 PER COPY
Copyright, 1938
AND
PUBLISHED ANNUALLY BY
AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS
51 MADISON AVENUE .'. NEW YORK, N. Y.
"TO THE isth EDITION
J^HE acceptance of the HEATING, VENTILATING, AIR
CoxDiTi6>'i>:Gt GUIDE as an authoritative source of scientific infor-
mation on all engineering phases of the industry, has imposed each year
since 1922 more and greater responsibilities on the Guide Publication
Committee. Although extensive new material has been added to this
edition, the ideals of the founders have been carefully preserved by pre-
senting only authentic and current investigative results which have been
tried and accepted in practice.
The sequence and arrangement of the various chapters have been
changed to provide for a more logical grouping according to related
subject matter, and a visual chapter index has been added. Probably,
the greatest changes that have been made in the text are those relating
to cooling phases of the industry. The chapters on Refrigerants and Air
Drying Agents, Cooling Load, Central Systems for Cooling and Dehu-
midifying and Cooling and Dehumidification Methods have been entirely
revised to bring them up-to-date and to correlate them more closely.
One entirely new chapter on Air Conditioning in the Treatment of
Disease was introduced in this edition which outlines many of the appli-
cation requirements found in the medical field. Some minor changes were
made in the chapters on Heat Transmission Coefficients, Air Leakage,
Heat and Fuel Utilization, Heating Boilers and Steam Heating Systems.
The chapters have been rewritten which deal with Air Pollution,
Automatic Fuel Burning Equipment, Hot Water Heating Systems and
Piping, Spray Equipment for Humidification and Dehumidification, Air
Cleaning Devices, Railway Air Conditioning, Industrial Air Conditioning,
Piping and Duct Insulation, Electrical Heating and Radiant Heating.
The Catalog Data Section of the GUIDE is receiving more recognition
as each issue appears for the valuable product data contained therein.
As usual, the manufacturers have cooperated in accomplishing the dual
purpose of this part of the GUIDE; to provide authoritative and condensed
catalog information for the Guide user, and to develop an effective and
productive advertising medium for the manufacturer.
In offering the 16th edition of the HEATING, VENTILATING, AIR CON-
DITIONING GUIDE, the Committee wishes to acknowledge not only the
editorial assistance unselfishly given by many whose aid is specifically
accredited elsewhere, but also the valuable suggestions offered by the many
readers and users of other editions. It is hoped that improvements
and additions will be suggested to future Committees by readers of
this volume, particularly, as perfection is not of human attainment.
Without the publication of previous editions, the issuance of the
HEATING, VENTILATING, AIR CONDITIONING GUIDE 1938 in this fairly
complete state m so short a time would be practically impossible. It is
the Committee s^hope that the same enthusiastic reception* given to
earlier volumes will be accorded this edition of 15,500
:V, Chairman
#
GUIDE PUBLICATION COMMITTEE
CONTENTS
HEATING • VENTILATING • AIR CONDITIONING • GUIDE 1938
PAGE
TITLE PAGE i
PREFACE.- ii
CONTENTS iii-v
EDITORIAL ACKNOWLEDGMENT iv
CODE OF ETHICS FOR ENGINEERS vi
INDEX TO TECHNICAL DATA vii
TECHNICAL DATA SECTION 1-840
CATALOG DATA SECTION 841-1162
INDEX TO ADVERTISERS 843
INDEX TO MODERN EQUIPMENT „ 1165
ROLL OF MEMBERSHIP. 1-80
SECTION I. PRINCIPLES
Chapter 1. Air, Water and Steam... 1
Chapter 2. Refrigerants and Air Drying Agents 35
Chapter 3. Physical and Physiological Principles of Air Conditioning.... 51
Chapter 4. Air Pollution... _ 79
SECTION II. BASIC DATA AND COMPUTATIONS
Chapter 5. Heat Transmission Coefficients and Tables..™ 89
Chapter 6. Air Leakage. 121
Chapter 7. Heating Load 133
Chapter 8. Cooling Load 147
SECTION III. COMBUSTION AND UTILIZATION OF FUELS
Chapter 9. Fuels and Combustion 165
Chapter 10. Chimneys and Draft Calculations 179
Chapter 11. Automatic Fuel Burning Equipment 201
Chapter 12. Heat and Fuel Utilization 229
SECTION IV. STEAM AND HOT WATER HEATING SYSTEMS
Chapter 13. Heating Boilers 243
Chapter 14. Radiators and Gravity Converters... „ 263
Chapter 15. Steam Heating Systems 276
Chapter 16. Piping for Steam Heating Systems.- 301
Chapter 17. Hot Water Heating Systems and Piping 331
Chapter 18. Pipe, Fittings and Welding 35£
(Continued on Page V)
EDITORIAL ACKNOWLEDGMENT
T70R 16 years the HEATING, VENTILATING, AIR CONDITIONING GUIDE
I/ has been published by the AMERICAN SOCIETY OF HEATING AND
VENTILATING ENGINEERS and it retains its leadership asjthe authoritative
reference volume of the profession and its allied industries. Its users are
legion and they have adopted The Guide as their standard reference
source because they recognize that the data are unbiased, up-to-date and
readily usable. This has been made possible because of the willingness of
hundreds of technical experts to contribute freely from their knowledge
and practical experience for the advancement of the profession.
To the following individuals the Guide Publication Committee is
profoundly grateful for their assistance in the production of the 1938
edition, and also to those former contributors who have previously
prepared a firm foundation for the addition of new material.
H. E. ADAMS
T. N. ADLAM
. C. ALBRIGHT
!. L. ALT
0. W. ARMSPACH
C. L. ARNOLD
C. M. ASHLEY
PROF. LL. BEAL
F, R. BICHOWSKY
J. L. BLACKSHAW
M. G. BLUTH
C. A. BOOTH
C. J. BRAATZ
C. E. BRONSON
PROF. A. I. BROWN
C A. BULKELEY
W. H. CARLTON
P. D. CLOSE
SABIN CROCKER
R. C. CROSS
D. N. CROSTHWAIT, JR.
PHILIP DRINKER
G. G. EARLY, JR.
E. V. ERICKSON
C. E. ERNST
JOHN EVERETTS, JR.
PROF. M. K. FAHNESTOCK
W. L. FLEISHER
W. G. FRANK
J. E. GODFREY
C D. GRAHAM
W. A. GRANT
'. R. HERTZLER
:. G. HILLIER
F. C. HOUGHTEN
PROF. C. M. HUMPHREYS
H. F. HUTZEL
L. P. HYNES
A. J. JOHNSON
E. F. JONES
C. F. KAYAN
R. T. KERN
R. E. KEYES
PROF. V. O. KNUDSEN
PROF. S. KONZO
PROF. A. P. KRATZ
PROF. G. L. LARSON
L. L. LEWIS
S. R. LEWIS
H. A. LOCKHART
ARTHUR MCCUTCHAN
PROF. L. G. MILLER
PROF. P. E. MOHN
L. L. MUNIER
,H. C. MURPHY
PROF. D. W. NELSON
P. NICHOLLS
R. F. NORRIS
A. J. OFFNER
0. W. OTT
k:
:S. PARKINSON
. G. RAPPOLT
PROF. T. F. ROCKWELL
J. 0. Ross
S. I. ROTTMAYER
PROF. F. B. ROWLEY
. S. SANDFORT
:OF. W. M. SAWDON
PROF. L. E. SEELEY
LESTER SEELIG
C. G. SEGELER
A. M. SELVEY
C. D. SHIELDS
R. W. SHIELDS
A. L. SIMISON
D. C. SIMPSON
T. H. SMOOT
A. E. STAGEY, JR.
D. J. STEWART
C. A. THINN
R/ J. THOMPSON
W. W. TIMMIS
PROF. G. L. TUVE
. H. VAN ALSBURG
'. 0. URBAN
A. R. WALKER
J. H. WALKER
PROF. G. B. WILKES
M. S. WUNDERLICH
PROF. C. P. YAGLOU
The members of the Society are especially indebted to these engineers
who have aided in the preparation of this volume and the Guide Publi-
cation Committee hereby expresses its appreciation for the loyal coopera-
tion of the many contributors to this 16th edition.
GUIDE PUBLICATION COMMITTEE
ALBERT BUENGER, Chairman
S. H. DOWNS
C. H. B. HOTCHKISS
E. N. MCDONNELL, Advisory
S. S. SANFORD
W. H. SEVERNS
JOHN JAMES, Technical Assistant
CONTENTS (Concluded)
SECTION V. AIR SYSTEMS PAGE
Chapter 19. Gravity Warm Air Furnace Systems 377
Chapter 20. Mechanical Warm Air Furnace Systems 393
Chapter 21. Central Systems for Heating and Humidifying 409
Chapter 22. Central Systems for Cooling and Dehumidifying 423
Chapter 23. Unit Heaters, Ventilators, Air Conditioning, Cooling Units 435
Chapter 24. Cooling and Dehumidification Methods „ 469
Chapter 25. Spray Equipment for Humidification and Dehumidification,. 499
Chapter 26. Air Cleaning Devices 519
Chapter 27. Fans 531
Chapter 28. Air Distribution 547
Chapter 29. Air Duct Design.- 563
Chapter 30. Sound Control 583
SECTION VI. GENERAL
Chapter 31. Air Conditioning in the Treatment of Disease 597
Chapter 32. Railway Air Conditioning 60S
Chapter 33. Industrial Air Conditioning 62]
Chapter 34. Industrial Exhaust Systems 63c
Chapter 35. Drying Systems 64'
Chapter 36. Natural Ventilation.- 669
Chapter 37. Automatic Control 683
Chapter 38. Motors and Controls 703
Chapter 39. Piping and Duct Insulation 719
Chapter 40. Electrical Heating 741
Chapter 41. Radiant Heating 753
Chapiei" 42 District Heating™ 765
Chapter 43. Water Supply Piping and Water Heating 783
Chapter 44. Test Methods and Instruments.. 807
Chapter 45. Terminology 819
CODE of ETfflCS for ENGINEERS
ENGINEERING work has become an increasingly important factor
in the progress of civilization and in the welfare of the community.
The engineering profession is held responsible for the planning, construc-
tion and operation of such work and is entitled to the position and
authority which will enable it to discharge this responsibility and to
render effective service to humanity.
That the dignity of their chosen profession may be maintained, it is
the duty of all engineers to conduct themselves according to the principles
of the following Code of Ethics:
1 — The engineer will cany on his professional work in a spirit of fairness
to employees and contractors, fidelity to clients and employers, loyalty
to his country and devotion to high ideals of courtesy and personal
honor.
2-— He will refrain from associating himself with or allowing the use of his
name by an enterprise of questionable character.
3 — He will advertise only in a dignified manner, being careful to avoid
misleading statements.
4 — He will regard as confidential any information obtained by him as to
the business affairs and technical methods or processes of a client or
employer.
5 — He will inform a client or employer of any business connections, in-
terests or affiliations which might influence his judgment or impair the
disinterested quality of his services.
6 — He will refrain from using any improper or questionable methods of
soliciting professional work and will decline to pay or to accept com-
missions for securing such work.
7 — He will accept compensation, financial or otherwise, for a particular
service, from one source only, except with the full knowledge and
consent of all interested parties.
8 — He will not use unfair means to win professional advancement or to
injure the chances of another engineer to secure and hold employment.
9 — He will cooperate in upbuilding the engineering profession by exchang-
ing general information and experience with his fellow engineers and
students of engineering and also by contributing to work of engineering
societies, schools of applied science and the technical press.
10— He will interest himself in the public welfare in behalf of which he will
be ready to apply his special knowledge, skill and training for the use
and benefit of mankind.
INDEX
HEATING VENTILATING Am CONDITIONING
GUIDE 1938
Technical Data Section
Chapters 1-45 and Pages 1-840
Abbreviations, 831
Absolute humidity, 8, 819
Absolute pressure, 807, 819
Absolute temperature, 819
Absolute zero, 819
Absorption, (sec also Regain)
agents, 44
as means of dehumidification, 492
by building materials, 155
of solar radiation by glass, 152
of sound, 592
system, 492, 493
Acceleration, 819
due to gravity, 819
Acclimatization, 56
Acoustics, acoustical, 583
treatment, 591
Activated alumina, 39
Adiabatic saturation, 11, 495, 502, 819
driers, 649
Adjustable speed motor, 704, 709, 710
Adsorption, 819
agents, 37
as means of dehumidification, 490
systems
alumina, 491
silica gel, 491
Air
adiabatic saturation of, 11
amount per person, 70
atmospheric, 1
changes of, indoors, 51, 129
cleaning devices, 519, 819
A.S.H.V.E. code for, 519
requirements of, 519
types of, 520
composition of, 1, 51
density of, 6
distribution of, 72, 397, 547
balancing, system, 560
for comfort, 69
effect of turning blades, 554
factors in room cooling, 552
factors in room heating, 554
grille locations, 547
natural ventilation, 669
railway air conditioning, 560, 610
residence, 397
with unit air conditioners, 455
with unit heaters, 441
with unit ventilators, 446
dry, 1, 4, 8, 59, 822
drying agents, 35, 37
ducts, 563, (see also Ducts, Air)
excess, 168
exfiltration, 121, 413
filtration, 121, 180, 229, 413, 820
Air (continue<f)
flow, 72, 77
control, principles of, 675
formulae, 563
into a hood, 638
loudness chart, 556
natural, measurement of, 678
requirements, 676
through openings, 670, 675
friction of, in pipes, 567, 568
impurities in, 79, 676
size of, 80
ionization of, 75
leakage, 121, 127
minimum outdoor, requirements, 7S
mixtures with water vapor, 12
moist, 68
motion, 72, 74
movement, measurement of, 811
odors in, 51
optimum conditions, 62
indoors in summer, 68
outlet noises, 554
outside, introduced,
fan systems, 414
through cracks, 126, 129
through doors, 127
unit air conditioners, 455
unit ventilators, 447
pollution, 79
abatement of, 84
effect on health, 83
primary, 167
properties of, 3, 4
for combustion, 167, 176
for ventilation, 70, 609
recirculation of, 77
fan systems, 411, 417
unit ventilators, 447
saturated, 1, 5, 10, 827
secondary, 167
space conductances, 93
speeds to convey material, 642
standard, 828
summer, conditions, 68
still, 57
synthetic chart, 829
velocity, (see Velocity, Air)
vitiation, 51
volume, 12
washer, 499, 820, (see also Washer, Air)
operation of, 690
saturation efficiency, 502
weight of, 6
Air conditioning 51, 503, 819, (see also Air)
air change per occupant, 71
chemical factors, 55, 81
comfort chart, 63, 64
in disease treatment, 597
Vil
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Air conditionin
, -V.»7
with, ice, V,,<»}
,
tus for, .503
automatic control. <»83
exhaust aystems, t>33
operation cf, 485
process conditions, G21
unit coolers, 449
objective of, 1
physical factors, 51
redrcalation, 77, 411. 417, 447
symbola, 836
units, 451
Algae formations. 514
Allergic disorders, 004
classification of, 601
treatment cf,
apparatus for, 604
limitations in, 605
Alternating current motor, 703
Altitude. 1S3
Alumina system of adsorption, 30, 491
Aluminum foil, 94
Aluminum oxide, 39
Ammonia, 35, 36, 511
Anemometer, 812. 820
Anesthesia, 597
apparatus, 507
effect of, 598
inflammability, 598
Anthracite, 165, 169, (see also Coal)
stokers, 205
Apartment bouses,
hot water supply to, 797
steam consumption, 234
stokers suitable for, 206
Appendicitis, 599
Artheritis, 607
A.S.H.V.E. Codes and Standards, 247. 281, 518,
534. 680, 839
A.S.M.E. boiler construction code, 257
Artificial fever, 602
conditions for, 603
diseases treated, 603
limits for. 603
production of, 603
Asbestos, 725
Ash*
cared for by stokers, 201
fly, 79
Asphyxia, 605
Asthma, 604, 605
Atelectasis, 605
Atmosphere, standard, 807
Atmospheric steam heating system, (see also
Steam Heating Systems)
Atmospheric water cooling apparatus, 507
design of, 510, 511
efficiency of, 512, 516
Atomization,
for humidifying. 504
of 02, 214
Attic fans. 464
Automatic control, 399, 608. (see also Controls)
Automatic fuel burning equipment, 201
Awnings, 156, 406
Arm! velocity formula, for hoods, 637
B
Babcock's formula for steam flow, 301, 766
Baby care, (see Nurseries)
Baffles, 595, 820
Balancing air distribution system, 560
Barn ventilation 679
Barometer,
aneroid. 808
mercurial, 807
Barometric pressure, 183, 807
Baudelot,
chamber, 502
cooler, 496
Bends, expansion, 362
BET, British equivalent temperature, 356
Biochemical reactions, control of, 628
Bituminous coal, 165, 171
Blast, 820
Blower, blowers, 531, (see also Fans)
standard test code for, 534
Body,
human, surface area, 71
odors, 71
Boiler, boilers, 243, 820
allowances, 252, 802
A.S.H.V.E. test codes, 248, 840
A.S.M.E. construction code, 258
baffles, 395, 820
capacity, 243, 442
care during summer, 261
cast-iron, 243
cleaning, 260
codes, 248
combustion rate, 244
connections, 258, 316
controls, 698
conversion, 218, 256
design of, 246
domestic oil burners, 218
draft loss through, 189
efficiency of , 247, 251 m
for electric steam heating, 745
erection of, 259
fittings, 258
gas-fired, 222, 245, 256
grate area, 255
heat transfer rates, 247
heating, surface, 247, 820
horsepower, 251, 820
installation, 256. 259
insulation. 261
limitations, 257
low pressure, construction code, 258
maintenance, 259
oil burners, 4, 218
operation, 259
output, 250
performance curves, 254
pick up, 252
pipe tax, 253
ratings of, 248, 249
run out sizes, 319
scale in, 260
selection of, 251, 254, 255
settings, 218, 246
for mechanical stokers, 211
special. 245
steel, 243
troubles with, 260
types of, 240
warming-up allowance, 252, 254
water line, 258
Boiling point of water, 27
Booster,
coils, 411
fans, 390, 426
Booths, spray, 640
Bourdon tube, 808
Boyle's law, 7
Brake horsepower, heat equivalent of, 141
Breeching, draft loss through, 193
Brine, 454, 483
British equivalent temperature, 756
British thermal unit, 820
Building, buildings,
absorption coefficients, 155
air velocities in, 569
ALPHABETICAL INDEX TO TECHNICAL DATA SECTION
Building, buildings (continued)
classification, for district heating, 777
construction, heat transmission of, 91, 97
district heating, 770
fuel requirements of, 229
hot water supply to, 794, 797
intermittently cooled, 149
intermittently heated, 141
load factors, 240
materials, heat transmission of, 97
noise in, 5S7
saving of steam in 771
steam consumption, 234
tall, infiltration in, 128
water supply to, 783
Burner, burners,
automatic equipment, 201
coal, 201
conversion, 224
gas, 221
oil, 213
By-pass method, 425, 820
Cabinets, (see Enclosures)
Calorie, 820
Calorific values,
coal, 166
gas, 176
oil, 174
Capacitor motor, 706
Capillary moisture, 651
Carbon dioxide, 36
concentration in air, 72
as corrosion agent, 374
as an Index of,
combustion, 168, 176, 212, 220, 224
draft loss, 192
odors, 52
measurement of 815
as a refrigerant, 38
Carbon monoxide,
in air, 84
in garages, 681
produced by gas, 224
produced by oil burners, 220
produced by stokers, 212
Carnot cycle, 475
Cattle, heat and moisture produced by, 678
Ceilings, heat transmission, 111
Central air conditioning systems, 423
classification of, 423
cooling cycle control for, 691
design of, 427
location of apparatus, 428
ratings of, 429
spray type, 424
zoning, 428
Central fan heating systems, 409, 688, 820
computations for 413
design of, 413
electrical, 744
heating cycle control for, 688
heating requirements of, 412
Characteristics of motors, 708
Charles* law, 7
Chemical reactions, control of, 628
Chimney, chimneys, 179
areas of, 187, 189, 191
characteristics, 182
construction of, 195
effect, 129, 670, 672
for gas heating, 196
gas temperature, 184
performance, 186
sizes, 187, 189, 191, 198
Venturi, 180
Chorea, 603
Cleaners, air, (see Air, Cleaning Devices)
Clearance, window sash, 124
Climatic conditions, 138
Coal, (see also Anthracite, Coke, Lignite)
air speed for conveying, 642
analysis of, 165
bituminous, 165, 171
burning rate chart, 238
calorific value, 166
classification of, 165
dust, disposal of, 79
dustless, 172
pulverized, 172
semi-bituminous, 165, 172
size of, 169
Coal burning systems,
automatic control of, 699
automatic firing equipment, 201
boilers, 243
combustion rate, 394
draft required for, 192
fuel requirements, calculation, 230
furnace requirements, 395, 400
hand-fired, 173
stokers, 201
Codes,
A.S.H.V.E. codes and standards, 839
for grinding, polishing, and buffing wheels, 636
for proportioning warm air heating plants, 222
for rating air conditioning equipment, 435, 462
for use of refrigerants, 426
Coefficients of heat transmission, (see Heat Trans-
mission, Coefficients)
Coils,
booster, 411
cooling, 406, 453
evaporator, 406
heating, 404, 411
hot water, 404
pipe. 323
preheater, 411
radiator, 263
reheater, 411
steam, 411
tempering, 411
Coke. 166, 210, 411
combustion of, 172
Cold, effects on human body, 55
Collectors, dust, 643
Column radiator, 821
Combined system,
air conditioning equipment, 423
central fan, 409
Combustion, 165 •
air required for, 167, 168, 176
constants, 659
of different coals, 169, 171, 209
in driers, 655
of gas, 176, 224
of oil, 219
rates for heating boilers, 244
smokeless, 247
with various stokers, 209
Comfort, 57
chart, 64
conditions of, 147
effective temperature, 60, 61, 62
heating for. 753
level, 267
line, 63. 66, 821
for men working, 66
optimum air conditions for, 62
school children, 65
zone, 62, 821, (see also Zone, Comfort)
Compensated cooling control, 693
Composition of water, 27
Compound wound motor, 703
Compressed air, 504
Compressors, 470
control of, 701
reversed refrigeration 495, 749
types of, 471
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Condensation,
4>n balidin* surface*, 1*1
metew, 773
prevention of, 141, 734
rate in radiators, 267
return pumps, 2tal
in steam beating systems, 275, 301
Condenser, 48 1
design data, 481, 511
performance of, 481
turbine, 507
types cf, 481
water temperatures, 511
Conditioning and drying, 627, (s« also Atr Condt-
tionint)
Conductance, 90, 92, 821
of air maces, 90, 93
of building materials, 97
of insulation. 97, 723
surf ace. 92
Conduction, 263, 821
drying by, 647
beater. 742
Conductivity, 90. 92. 821
Conductor, 821
Conduit, 707
Constant relative humidity. 821
Constant speed motor, 704, 70S, 709
Constant temperature drier, 650
Construction code for low pressure boilers, 258
Contours, velocity, 637
Control, controls, 683 821
of air conditioning equipment. 485. 683, 688, 700
combined system, 688
split system. 689
apparatus, 684
automatic, 399. 683. 697. 698
gas burner. 698
oil burner, 698
stoker, 699
compensated cooling. 693
of cooling; units. 695
domestic hot water, 700
of draft, 181
of electric motors, 711
electric system, 686
of electrical heating. 750
of fans, 541
modulating, 687, 745
moisture content. 625
of natural ventilation, 399, 673
of noise, 584
of ofl burning; equipment, 698
pneumatic system, 686
positive acting, 686
pressure, 685
railway systems. 612, 613
rate of biochemical reactions 628
rate of chemical reaction, 628
rate of crystallization, 629
" " " " quipment, 701
of refrigeration equi
compressor, 701
vacuum, 701
weft water, 702
of regain, 624
of relative humidity, 685
residential, systems, 699
room, 687
self-contained, system. 686
of sound, 583
of steam V^t*"g gys^rns, 291
of temperature, 220, 683, 750
types of, 686
wut. 220.683, 750
of vacuum pomps, 295
rone, 291, 688
Convection, 821
Gosmctor*, 263, 268, 821
A^H.V.E* code for, 271
connections for, 322
correction rating factors, 271
design of, 269
drying by. 649
Convectors (continued)
gravity, 263
heat emission by, 270
heating capacity. 270 .
performance characteristics, 270
selection, 270
Conversion burners, 224
Conversion equations, 833
Coolers,
surface, 431
types of 483
unit, 435, 449
Cooling, 11, 24
with central fan heating systems, 406, 423, 485
design, system. 407, 427
effect, 10
effective temperatures for, 68
by electric refrigeration, 470. 749
equipment, design of, 507
evaporative, 423, 483, 501
of fluids, 511
of human body, 147
load, 147
with mechanical warm air systems, 407
methods, 406, 423, 469
ponds, 512
railway air conditioning, 411
relative humidities for, 68
spray, 469
surface, 469
towers, 482, 512
units, thermostatic control, 695
water, 507
Copper pipe, 356
heaUoss, 721
Corrosion,
of boilers, 261
of industrial exhaust systems, 645
protective materials, 646
inhibitors, 375
of pipe, 374
tester, 375
Costs,
of attic fans, 460
of district heating service, 778
of railway air conditioning, 617
of unit conditioners, 464
Crack, window, 124
Crystallization, control of, 629
Cyclone dust collector, 643
Dalton, law of partial pressures, 1
Damper, dampers,
apparatus which operates, 683
control, 673
in duct systems, 398
motors, 685
types of, 398
Decibel, 583, 822
Definitions, 68
Defrosting coils, 450
Degree-day, 822
base temperature for, 234
methods of estimating fuel consumption, 231
records for cities, 232
Degrees, perspiration, 73, 75
Dehumidification, 11. 419, 469, 822
by absorption. 492
by adsorption, 490
effective temperatures for, 66
methods of, 423, 453, 490
by refrigeration, 469
relative humidities for, 68
Dehumidifier, dehumidifiers, 169
alumina, 491
in central air conditioning systems, 424
in industrial air conditioning, 503
silica gel, 491
types of, 453, 507
ALPHABETICAL INDEX TO TECHNICAL DATA SECTION
Density, 3, 822
of air, 6
of saturated vapor, 12
specific, 3
of water, 27
Dennatitus, 604
Design conditions in industrial conditioning, 621
Design temperature,
dry-bulb, 138, 147
wet-bulb, 147, 511
Dew-point, 822
relation to relative humidity, 9
temperature, 2
Diameter, circular equivalents of rectangular
ducts, 572
Diarrhea, 600, 601
Dichlorodifluoromethane, 35, 40, 473, 511
Diffuser, 822
Diphtheria, 52
Direct current motor, 703
Direct-indirect heating unit, 822
Direct radiator, 822
Direct return system, 332, 822
Dirt pockets, 328
Disc fans, test code for, 524
Disease treatment,
air conditions for, 599, 600, 603
allergic disorders, 604
anesthesia, 597
artificial fever, 602
classification of diseases, 602, 605
diseases treated, 52, 599, 600, 603, 604, 605, 607
explosion hazard, 597
fever therapy, 602
filtering in, 600
hospital air conditioning, 597, 607
nurseries, 600
operating rooms, 597
oxygen therapy, 605
premature infants, 600
satisfactory air conditions, 599, 600. 603
sterilization of air, 650
ventilation rates, 598, 602
Distribution of air, 547, (see also Air, Distribution}
District heating, 765
building connections, 770
conduits, 767
economies in, 770
meters, 774, 775
pipe, (see also Piping}
distribution, 765
returns, 767
sizing, 766
rates, 778
steam consumption, 777
tunnels, 769
Diverter, back draft, 196
Domestic oil burners, 215
Domestic stokers, 204
Domestic supply,
hot water, 747, 799
control, 700
load, 253
water, 783
Doors,
air leakage through, 127
coefficients of transmission of, 117
natural ventilation through, 672
Down-feed piping systems, (see Steam Healing
Systems)
Draft, 179
available, 182, 186
back, diverter, 196
dimensions, 196
calculations, 179
capacity, 181
control, 181
equation, 187
Draft (continued)
mechanical, 180
natural, 179
requirements, 169
theoretical, 182
Drain connections, 259
Drawing, symbols for, 836
Drip, 822
Dripping of steam pipes, 327
Drum driers, 648
Dry air, 822
Dry-bulb temperature, (see Temperature, Dry-bulb)
Dry return, 823
Driers, 648, 649
adiabatic, 649
agitated, 648
batch, 648
compartment, 648
continuous, 648
cylinder, 648
design, 658
drum, 648
festoon, 648
high temperature, 663
induction, 648
intermittent, 648
rotary, 648
spray, 648
tower, 648
tunnel, 648
vacuum, 648
Drying, 627, 647, (see also Regain)
adiabatic temperature, 649
air circulation in, 653
combustion, 655
by conduction, 649
constant temperature, 650
by convection, 649
design, 658
direct contact, 649
equipment for, 653
estimating method, 665
factors influencing, 651
gas combustion constants for, 659
high temperature, 652, 663
humidity in, 652
humidity chart, 654, 655
industrial, 627, 647
low temperature, 652
mechanism of, 650
methods of, 647
moisture in, 651
omissions in the cycle, 650
by radiation, 647
rules for, 652
stages of moisture diffusion, 650
constant rate period, 650
falling rate period, 650
sun, 647
temperature in, 652
time of, 653
materials, 656
ventilation phase, 661
Duct, ducts
air, 398, 563
design of, 563
equal friction method, 569, 575
velocity method, 569
for air distribution, 547
air velocities in, 401, 642
circular equivalents, 572
construction details, 580, 641
' ' of duct systems, 398, 569, 578, 634, 640,
head, 822
intensity required, 167, 190
losses, 190
in chimneys, 192
through fuel bed, 190
heat loss from, 732
humidity measurement in, 814
insulation of, 719, 732
lining factor for sound, 592
noise transmission through, 592
pressure loss in, 564
elbows, 564, 642
for recirculated air, 381
resistance, 643
sheet metal for, 580, 642
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Duct, ducts •coxiinutft
suca of, 367, 571, 633
temperature lose in, 415
temperature measurement in, 809
velocity measurement in, 811
Duit, 7W, 823
air speeds to convey, 635, 642
catching devices, So
collectors, 643
concentration in air, 82, 815
counter, SIo
disposal of, SO
Industrial exhaust systems, 633
measurement cf, 815
Dynamic equilibrium, Carrier's equation for, 2
Dynamic head. 823
Dysenterfa, 52
E
Eczema, 604
EDR, equivalent direct radiation, 828
Effective temperature, (see Temperature, Effective)
Ether, 81, 579
Elbow, elbows,
design of. 367, 398
equivalents, 340
Ion of pressure in, 564
resistance in, 643
sheet metal used in, 641
welding of. 368
Electric, electrical,
automatic, control system, 686
central fan heating systems* 744
control, motor, 703
current, as corrosion agent, 374
heat equivalent, 141, 160. 750
heating, 741
auxiliary, 749
cost of .750
of hot water, 747
industrial, 748
heaters, 742
conduction, 742
gravity convection, 743
radiant, 743
heating elements. 252, 742, 743
with unit heaters, 743
lamp bulbs, heat from, 160
motors, 703
resistors, 742
Eliminator plates and baffles, 499
Enthalpy, 22, 823
Entropy, 473, 478, 823
tables, 36, 38, 40, 42, 44
Equations, conversion, 833
dynamic. 2
hygroscopic, 626
Equipment noise, 586
Equipment room, design of, 591
Equivalent, equivalents,
circular, 572
direct radiation, 304, 601, 828
tiljow, 340
evaporation, 251, 823
heat, 823
of air infiltration, 140
of brate horsepower. 141
electrical, 833
mechanical, 826
length of run, 305
square feet, 264
Kitfimated design load, 823
Estimated marmiTTTn load, 823
Estimating driers, 665
Estimating fuel consumption, 229
Etfaytene. 567
Eupatheoecope, 762, 817
Evaporation, 516
equivalent, 251
from human body, 54, 74
from water pans, 268
Evaporative condensers, 483
Evaporative cooling, 423, 483, 495, 501
Evaporators, 483
Exfiltration, 121, 229, 413
Exhaust systems, 633
classification of, 633
collectors, 643
corrosion, protection against, 645
design procedure for, 634
ducts for,
construction of, 641
design of. 640
resistance in, 643, 644
efficiency of, 645
fans for, 645
filters for, 644
flexible, 640
hoods for, 637
air flow in, 638
axial velocity formula for, 637
chemical laboratory, 640
large open, 639
velocity contours in, 637
industrial. 633
lateral, 637
motors for, 645
spray booth, 640
suction requirements, 635
velocity requirements, 635, 642
Expansion,
of joints, 315, 767
of pipe, 315, 359, 767
in steam piping, 767
tanks, 349
Explosion hazard,
inflammability of gases, 81
in operating rooms, 597
Exposure factors, 140
Extended heating surface, 823
Extended surface heating unit, 823
F
Fan, fans, 531
A.S.H.V.E. test code for, 534
attic, 464
booster, equipment, 390, 426
control of, 541
designation of, 543
drives, arrangement of, 542
for drying, 540
for dust collecting, 541, 645
dynamic efficiency of, 533
efficiency of, 533
in electrical heaters, 744
furnaces, 393
for gas-fired furnaces, 222
induced draft, 180
for industrial exhaust systems, 645
mechanical draft, 180
mechanical efficiency of, 533
motive power of, 543, 706
control of, 703
operating characteristics, 180, 533
operating velocities. 539, 540
performance of, 531, 539
quietness of, 442
ratings of, 538
selection of, 396, 538, 541, 543, 645
static efficiency of, 533
system characteristics, 537
systems of heating, 409
tip speeds, 538
total efficiency of, 533
types of, 393, 531, 535, 539
in unit conditioners, 455
in warm air systems, 390, 396
ALPHABETICAL INDEX TO TECHNICAL DATA SECTION
Fatigue* human, 56
Fever therapy, (see Artificial Fever)
Filter, filters, 521
automatic, 523
cloth, 644
design of, 521
dry air, 524
hay fever air, 604
installation of, 525
resistance of, 396
for sound, 392
unit type, 521
viscous type, 521
Fire walls, 640
Firing rate, 169, 171
Fittings, 355, (see also Connections, Pipe)
areas of, 364
boiler, 258
copper, 365
flanged, 366, 723
lift, 287
screwed, 364
welding, 366, 370
Flame, with oil burners, 214, 219
Flanges, welding neck, 371, 372
Flexible materials, 589
Floors, heat transmission through, 111
~~ is analysis, 816
fluids,
of, 511
for flow of, 563
774
moisture of, 626
gages,
Force, 824
Forced-air heating system, design, 3
Forge shops, heat given off in, 675
Formulae,
conversion, 833
heat transmission, 91
Foundries, heat given off in, 675
of cooling water, 517
insulation against, 733
Friction,
of air, in pipes, 566, 567
in chimneys, 185
coefficients, 567
factors, 393
heads in pipes, 336
in heating units, 412
losses in ducts, 565, 567, 571
in water pipes, 791
Fuel, fuels, 165, (see also Anthracite, Coal, Coke,
Gas, Lignite. Oil)
bed. draft loss through, 189
burning equipment, automatic, 201
burning rate charts, 238
consumption. 229, 236
oil gages, 221
oil, heating value, 174, 660
oil specifications, 174
requirements,
of buildings, 236
degree-day method. 231
theoretical method, 230
utilization of, 229
Fumes, 79, 824
industrial exhaust systems, 633
toxicity of, 83
Fundamentals of heating and air conditioning, 1
Furnace, furnaces, 824
capacity, 383
design of, 173, 211, 246, 377, 383. 394, 400
door slot openings, 486
gas-fired, 222
hand-fired, 173
performance curves of, 385
types of, 221, 393, 403
volume, 824
for warm air systems, 393
Furnacestat, 399
fuel oil, 221
pressure, 824
steam, 258
vacuum, 808
Galvanometer, 809
Garage, garages,
air flow necessary in, 676
A.S.H.V.E. ventilation code, 679
heaters, for, 224
Gas, gases,
burner control, 698
burning rate chart, 239
calorific value. 141, 176
hi chimneys, 183
combustion constants, 659
constant for dry air, 8
flue, analysis, 816
fuel,
manufactured. 176
natural, 176
properties of, 176
inflammability, 81
requirements per degree day, 237
scrubbers, 86
toxicity of, 83
Gas-fired appliances, 221
automatic control of, 225, 698
boilers, 222, 245, 456
carbon monoxide produced by, 224
chimneys for, 196
classification, 221
combustion in, 224
conditioning unit, 462
control of, 225, 698
conversion burners, 224
furnace requirements for, 394, 900
heat from, 160
rate of gas consumption, 395
ratings of, 226
sizing, 225
types of space heaters, 223
used with unit heaters, 443
warm air furnaces, 222
Gaskets, 366
Glass,
heat transmitted through. 117, 152
solar radiation through, 152
Globe thermometer, 762
Glossary of terms, 819
Goitre, 599
Gonorrhea, 603
Grates, 824
areas of, 249, 255, 383, 402, 421, 824
of furnaces, 249, 255, 383, 402, 421
of stokers, 201
Gravity,
circulation, 345
converters, 263, 743
heat emission of, 263
gravity-indirect heating systems, 272
pressure heads, 344
specific, 3
steam heating systems, 275, (see also Steam
Heating Systems)
warm air heating systems, design of, 377
Grille, grilles, 824, (see also Registers)
anemometer readings through, 812
for concealed heaters, 270
redrculating, 381
of roof ventilators, 672
velocity through, 401
for warm air systems, 381, 397
Hartford return connection, 258, 278, 318
Hay fever, 604
Hazard of explosion, in operating rooms, 597
HEATING VEWTILATINO AIR CONDITIONING GUIDE 1938
Health. Sd, 8!M», f see also Disease Treatment)
Heart trouble, 605
Heat, 824
absorbed by bonding structure, 141
of adsorption. 43 f M
air infiltration equivalent of, 130
capacity, 155, 823
of leader pipe*, 378
of condensation, 45
conduction, 821
consumption, 224
content,
of air and water vapor. 2
of coal, 166
of dry air. 22
of gase*, 661
of saturated water vapor, 23
convection, 821
conversion equations, 833
demand, factors governing, 133, 241
effects on human body, 54
electrical equivalents of, 750, 834
of convectors, 263, 270
by radiation, 756
of radiators, 263, 270
equivalent, equivalents, 834
of air infiltration, 130
of brake horsepower. 140
electrical, 350. 834
exchanger. 507. 506
shell and tube, 481
flow meter, 817
gain*
from fixtures and machinery, 160
for insulated pipe, 735
from outside air, 158
to be removed. 430
infiltration equivalent of, 130
latent, 31, 828,
loss, 73, 76
of the liquid, 28, 825
loss,
from bare pipe, 719, 721
computation of, S9, 142, 750. 758
cost of. 720
determination of, 133, 140, 229, 753
from ducts, 730
effect of insulation on, 737
from human body, 73, 753, 755
by infiltration, 130, 229
latent, 73, 76
from piping of gas-fired furnaces, 225
by radiation, 61, 753
sensible, 73. 755
to unbeated rooms, 118
•vtvntjfaf \nf\i 675
mftTftTiiyp^ probable demand, 133, 241
of mixing. 47
Tru^f^r^fg] eQuivalent of, 826
produced by cattle, 679
produced by human body, 53
pump, 472, 749
radiant, 753
calculation of, 758
measurement of, 761
types of. 756
radiation, 743. 753
regulation in p*?", 53, 57
requirements, 229
sensible, 147. 827
of air, 12
loss, 73, 756
of water, 31
solar, 151
sources of, 745, 754
other than heating plant, 140, 149
specific, 31
total, 22. 829
of saturated steam, 28
transfer, 89
coefficients, 90
rate, 247
Heat (continued)
transmission, 89, 754
through air spaces, 91
through building materials, 91
calculations, 89
coefficients, 89, 96
of ceilings, 111
combined, 118
of copper pipe, 721
of doors, 117
of floors. 111
of glass walls, 117
of insulation, 97, 821
of partition walls, 110
of roofs, 114
of skylights, 117
of surface conductance, 92
of walls, 104
of windows, 117, 151
convection equation, 754
definition of terms used, 90
effects of solar radiation on, 151
formulae, 91
through glass, 116, 151
measurement of, 817
in surface coolers, 431
by surfaces not exposed to the sun, 149
symbols used in formulae, 90
tables, 89, 97
through ducts, 730
time lag, 155
utilization, 229
Heaters,
direct-fired, 443
for domestic hot water, 799
electric, 741
capacity of, 750
conduction, 743
convection, 743
radiant, 223. 743
space, 223
unit. 437, 743
wall, 222
Heating, (see also Heaf)
auxiliary, 749
district, 765
effect of radiators, 266
electrical, 741
elements, electric, 742
fundamentals of, 1
load, 133
medium, 825
radiant, 743, 753
railway air conditioning, 611
by reversed refrigeration, 472, 749
surface, 247, 825
square foot of, 828
symbols, 836
systems,
district, 765
electrical, 741
fan, 409
gravity warm air furnace, 377
hot water, 331, 825
mechanical warm air furnace, 393
radiant, 743, 753
steam, 275, 745
units,
blow-through, 411
central fan, 744
draw-through, 411
value, fuel oil, 660
water, 783
Henry and Dalton, law of, 375
Hoods,
axial velocity formula, 637
canopy, 639
for chemical laboratories. 640
design of, 634
for exhaust systems. 637
of furnaces, 395 •
open, 639
suction pressures at, 635
velocity pressures at, 637
ALPHABETICAL INDEX TO TECHNICAL DATA SECTION
Horsepower, 825
boiler, 251
brake, heat equivalent of, 140
Hospital air conditioning, (sec Disease Treat-
ment)
Hot box, 817
Hot plate, 817
Hot water, domestic
control of, 700
load, 253
' supply, 797
Hot water heaters, 245, 799
Hot water heating systems, 331, 825
electric, 720
forced circulation, 331, 337
gravity circulation, 331
installation of, 351
mechanical circulation, 333
Hot water piping, 331
Hotels,
steam consumption, 234
stokers suitable for, 201
temperatures of, in winter, 134
water supply, 783
Humidificatfon, 10, 499, 825
apparatus for, 503
atomization for, 504
effective temperatures for, 65
methods of, 452
relative humidities for, 68
for residences, 403
systems of, 503
with washer, 501
Humidifier, humidifiers, 466
atomizing, 504
with fan systems, 419
high-duty, 504
self-contained, 505
spray, 505
types of, 466, 503
Humidistat, 400, 825
Humidity, 8, 825
absolute, 8, 819
control, 685
railway air conditioning, 612
in drying, 652
in hospitals, 597
for industrial processing, 622, 623
measurement of, 814
optimum, 68
relative, 9, 827, (see also Relative Humidity)
in comfort zone, 63
effect on moisture regain, 625
relation to dew-point, 9
specific, 8, 825
Hygroscopic materials, 626
moisture content, 625
processing of, 627
regain, 626
Hygrostat, 825
Hypertension, 607
Hyperthyroidism, 607, 699
Ice, in air conditioning, 407, 454, 496
control of, 701
Inch of water, 825
Induction motor, 707, 710, (see also Motors)
Industrial,
air conditioning, 621
apparatus for, 449, 503
calculations, 629
air pollution, 79
control,
biochemical reactions, 628
chemical reactions, 628
crystallization, 629
moisture content, 625
of regain, 624
Industrial (continued)
cooling systems, 469
design conditions, 621
drying, 540, 627
electrical heating systems, 748
exhaust systems, 633, (see also Exhaust Systems)
general requirements, 624
heat sources, 141
temperatures and humidities for processing, 622,
623
unit heaters, 444
Infants, premature, 63, 65, 600
Infiltration, 121
average, 126
fuel utilization, 229
heat equivalent, 130
through shingles, 123
through walls, 122
through windows, 124
Inflammability of gases, 81
Institutions, water supply to, 804
Instruments, 807
[nsulation, 825
asbestos type,
corrugated, 725, 726
laminated, 727, 728
of boilers, 261
bright metal foil, 94, 95
building, 751
characteristics of, 97, 723
of conduits, 738
of ducts, 732
economical thickness, 736
with electrical heating, 715
heat transmission through, 97, 723
for low temperatures, 733
magnesia type, 724
of piping, 719
to prevent condensation, 141, 734
to prevent freezing, 733
reflective type, 94, 95
rock wool type, 729
of sound, 587
tables, 97, 724
thickness needed, 736
underground, 737
of vibration, 587
lonization of air, 75
Isobaric, 825
Isothermal, 7, 826
J-K
Joints, expansion, 315, 767
Kata thermometer, 811
Lag in heat transmission, 155
Latent heat, 31, 826
loss, 72
of water vapor, 12
Lateral exhaust system, 637
Leader pipes, 378
heat carrying capacity of, 379
size of, 379, 389
Leakage of air, 121, (see also Infiltration)
Lignite, 166
Liquid, heat of the, 28, 825
Lithium chloride system of adsorption, 46, 492, 493
Load,
building factors, 240
cooling, 147
design, 251, 823
heating, 133
hot water supply, 825
maximum, 824
radiation, 824
Low temperature insulation, 733
XV
HEATING VENTHATINO AIR CONDITIONING GUIDE 1938
M
Machinery,
as heat scarce. 140, 159
mountings vibration, 587
sound insulation of, 587
Magnesia insulation, 724
Manometer, 811, 826
Manual control, (see Controls')
Masonry materials, heat transmission through, 97
Mass. 826
Mb, 331, 826
Mbh, 331, 820
Mean radiant temperature, 754, 758
Mechanical,
draft towers, 515
equivalent of heat. 82G, 834
fuel burning equipment, 201
refrigeration, 35
ventilation, 77
warm air furnace systems, 391
air distribution, 397
design of, 400
register and grille locations, 397
Medical treatment, (see Diseases)
Mental trouble, 605
Mercurial thermometer, 809
Metabolism, 53, 73
Meters,
choice of .774
condensation, 771
fluid. 774
NichoUs heat flow, 817
steam flow, 776
types of, 774
water, disc, 789
Methyl chloride, 37, 42, 511
Metric units, 835
Micromanometers, 808
Micron, 79. 826
Mixture, air and water vapor, 12
Modulating control, 687
Moisture,
content,
of air, 72, 147. 503, 625
capillary or free, 651
of hygroscopic materials, 626, 651
loss by human body, 76
from outside air, 158
produced by cattle, 679
regain. fi9o>
Mol, 826
Monitor openings, 672
Monofluorotxichloromethane, 37, 44
Motive power. 703
Motors, electric, 703
adjustable speed. 704, 709
adjustable varying speed, 704
alternating current, 705
application of, 708
capacitor type, 706
characteristics of, 708
classification of, 708
compound round, 703
constant speed, 704, 708
control equipment for, 711
automatic, 712
manual, 711
multispeed, 714
pflot, 712
single phase, 716
slip ring, 715
damper, 685
direct current, 703
control of, 713
speed characteristics, 704, 708
as heat source, 159
induction,
automatic start, 710
capacitor start, 706
repulsion, 705
repulsion start, 707
slip;ring -wound rotor, 710
sQuirrd cage, 707
Motors, electric (continued)
polyphase, 707
selection of, 645
series wound, 703
shunt wound, 703
single phase. 706
special applications, 711
split phase, 707
synchronous, 711
varying speed, 705
MRT, mean radiant temperature, 754, 758
N
Natural draft towers, 515
Natural ventilation, 72, 669
Nervous instability, 607
Neurosyphilis, 603
Nicholls heat flow meter, 817
Noise, (see also Sound)
air outlet, 554
in buildings, 584, 587
control of, 584
through ducts, 592
through room wall surface, 591
with warm air systems, 396
equipment, 586
kinds of, 586
level,
acceptable, 585
of compressors, 471
of fans, 539
of unit heaters, 442
measurement of 584
through building construction 587
Nozzle, 499
air spray, 499
oil atomizer, 214
water spray, 499
Nurseries, 600
equipment for, 602
requirements for, 601
ventilation rate, 602
Odors, 69
of human origin, 51
concentration 70
removed by outside air, 71
Off peak heating, 748
Oil, oils,
atomization of, 507
burner, burners,
air for combustion, 214
air supply for, 214, 219
boilers, 216. 218
burning rate chart, 238
classification, 215
combustion, 218
for commercial use, 216
control of, 220, 698
design considerations, 219
for domestic use, classification, 214
efficiency of combustion, 220
flame with, 214
furnace requirements, 246, 394
ignition, 214
oil consumption, 229, 238
operation, 214
Orsat test, 220
specifications, 173
types of, 215
calorific value of, 174
classifications, 171
as corrosion inhibitor, 375
cost of, 175
gages, 221
ignition of, 174, 214
preheating, 217
specifications, 174
ALPHABETICAL INDEX TO TECHNICAL DATA SECTION
One-pipe steam heating systems, 275, 826
Steam Heating Systems)
Openings, 670
air inlet, 672
monitor, 672 . .
for natural ventilation,
location of, 675
resistance offered to flow, 676
size of, 669
types of, 670
Operating rooms,
Anesthesia, 597
explosion hazard, 597
humidification, 598
static electricity, 598
ventilation. 598
Orifice, orifices,
friction heads, 612
seam,
Orsat test apparatus, 212, 220, 224, 816
Outlets, (see also Registers, Grilles')
design and location of, 559
Oxygen, 375, 559
Oxygen therapy,
diseases treated, 605
oxygen chambers, 606
oxygen tents, 605
Ozone, 77
Paint,
effect on radiators, 265
soray booths, 640
temperatures and humidities for processing, 623
Panel radiation, 826
Panel warming, 827
Partial pressures, Dalton's law of, 1
Perspiration, 51, 54, 73, 75
Petterson-Palmauist apparatus, 815
Pipe, piping, 355
bare, heat loss from, 719
bends, 315, 362
capacities, (see Pipe, Sizes)
coil radiators, 263
conduit, 738, 767
connections, 316, 770, (see also Connections)
copper, 356
corrosion, of, 374
district steam, 765 .
dimensions of, 359 (see also Pipe Sizes)
expansion of, 315, 359, 767
fittings, 364, (see also Connections, Fittings)
for water supply, 788
welding fittings, 366
flanges, 370, 723
flexibility of, 359
freezing,
prevention of, 733
friction, 791
of air in, 566, 567
heads in, 336
gaskets, 366
hangers, 364
heat loss from 225, 719
for hot water heating systems, 331, 351
insulation of, 719
joints, 315, 769
leaders, 378
radiating surface, 722
radiators, 263
refrigerant, 484
scale in, 374
sizes,
for boiler runouts, 318, 766
for central fan systems, 323
for convector connections, 322
dimensions, 356, 359
for district heating, 766
for domestic hot water, 795
Pipe, piping, sizes (continued)
elbow equivalents, 340
equivalent length of run, 305
friction head, 337, 791
of orifices in unions, 343
for Hartford return connection, 318
for hot water heating systems, 335
for black iron, 337, 338
for copper tube, 337, 339
forced circulation systems, 337
gravity circulation systems, 345
for indirect heating units, 325
mains, 790
for pipe coil connections, 323
for radiator connections, 320
refrigerant, 484, 486
return, capacity of, 308. 767
steam, 302, 306, 307
underground, 767
tables. 306, 655
tees, 364
for underground steam, 767
for water supply, 787
weights, 361
steam, capacity of, 304
for steam heating systems, 275, 301, (see also
Steam Heating Systems)
supports, 364
sweating, 734
tax, 253
tees, dimensions of, 367
threads, 363, 365
tunnels, 767
types of, 355
underground,
insulation of, 737
steam, 767
for unit heaters, 442
valves, 370
water supply, 783
weights of, 356
welding, 366
Pitot tube, 811 . . . . im
Plastering materials, heat transmission through, 101
Plenum,
chamber, 827 nnn
systems, automatic control of, 688
Plumbing fixtures, 377
Pneumatic control system, 286
Pneumonia, 52, 599, 605, 607
Pollen, 605
Pollution of air, 83
Polyphase motors, 707
Ponds, cooling, 512
Positive acting control, 686
Post-operative pneumonia, 599
Potassium permanganate, 514
Potentiometer, 827
Power, 827
conversion equations, 833
electric, 750
supply for controls, 686
Precipitators, dust, 527
Premature infants, 600
humidity of, 601
mortality of, 602
requirements of, 601
Pressure, pressures,
absolute, 819
air
in heating unit, 412
measurement of, 811
atmospheric, 807, 820
for atomization, 504
automatic control, 685
barometric, 183, 807
basic, 3
controllers, 685
conversion equations, 833
drop, 566, 791
drop through refrigerant pipe, 486
dynamic. 823
loss throug
r pipe, 339, 486
ducts, 563, 643
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Pressure, pressure \.&
i ,
jurtial, Da I ton* a law of, 1
rcfnxeratintf piant, 4S*t>
of saturated vapor, 12
static, 421, 82$
steam,
in direct beating, 760
drop, 278, 302, 307
initial, 302
in oriiice systems, 290
saturated, 28
in sub-atmospheric systems, 2S9
total, 829
vapor, 31, 830
velocity, 83O
water, 27, 789
Prime surface, 827
Processing, 621
cooling systems, 469, 621 .
industrial, temperatures and humidities for, 622
of textiles, 626
unit heaters, 444
Propeller fans, test code for, 534
Psychrometer, 827
sling, 811
Psycfarometric,
chart, 25, 60, 61, 62, (back ewer)
for drier, 654
explanation, 25
tests, 59
Pulmonary disturbances, 605
Pump, pumps,
centrifugal, 334
characteristics, 181
circulating, 333
condensation return, 292
heat, 472, 749
vacuum, 293
Pyrometer, 810, 827
mercurial. 810
optical, 810
radiation, 810
thermo-electric, S10
0-R
Quality,
of air, 69, 70, 71
impaired by rerirculation 83
Quantity,
of air,
measurement of, 811
necessary for ventilation, 70. 71, 72, 158,
609, 675
of cooling water, 511
Radiant heaters, 743
Radiant heating, 753
physical and physiological factors, 753
Radiation, 827
by black body, 759
drying with, 647
equivalent direct, 304, 828
heat loss by, 63, 76, 754
by human body, 63, 76, 754
load, 252
ofjwpe,722
by radiators, 263
solar. 151, (see also Solar Heat)
occlusion of , 84
through glass, 152
through walls, 152
ultra-violet. 75, 82
Radiator, radiators, 263, 827
A^,H.V.E. code for, 271
column, 821
concealed, 821
condensation rate in, 267
connections. 320, 348
control of, 687
correction rating factors, 271
effect of saperheated steam, 265
enclosed, 267
gas-fired, 223
Radiator, radiators (continued)
heat emission of, 263, 270
heating capacity of, 270
heating effect of, 266
for hot water systems, 346
output of, 264
paint, effect of, 265
panel, 827
pipe coil, 203
ratings of, 264
recessed, 827
selection, 270
tube, 829
types of, 263
wall, output, 264
warm air, 223
Railway air conditioning, 609
air distribution, 560, 610
cleaning, 611
cooling equipment, 611
calculation of, load, 619
capacity, 612
costs, 617
heating, 611
humidity control, 612
power requirements, 613
tractive resistance, 615
temperature control, 613
ventilation, 609
Raoults law, 493
Receivers, alternating, 299
Refrigerants, 35, 827
ammonia, 36
carbon dioxide, 38
codes for use of, 426
dichlorodifluoromethane, 40
lithium chloride, 46, 47
methyl chloride, 42
monofluorotrichlorometbane, 44
water, 45
Refrigerating, capacity, 429, 475
Refrigerating plant, 24, 469
centrifugal, 478
compressor, 470, 512
operating methods, 485
size of, 429, 475. 485
steam jet system, 477, 512
types of, 471
Refrigeration,
characteristics, 481
curves, 480, 481
coefficient of performance, 475
carnot cycle, 475
compression ratio, 477
control of, equipment, 701
dehumidification by, 470
efficiency,
cycle, 475
ejector, 479
mechanical, 477 .
losses. 476
mechanical, 472
pipe sizing, 484
discharge, 486
liquid, 487
suction, 488
practical cycle, 475
reverse cycle, 749
limiting factors, 749
systems,
absorption, dosed, 493
centrifugal, 479
mechanical, 496
steam ejector, 477
various types, 469
theoretical mechanical cycle, 473
theoretical work per pound, 474
ton of, 429, 475, 829
ton days of, 829
unit of, 429, 475
Regain,
control of, 624
of hygroscopic materials, 626
Registers, 827, (see also Grilles)
with gas-fired furnaces, 223
with gravity furnace systems, 381
ALPHABETICAL INDEX TO TECHNICAL DATA SECTION
Registers (.continued') .
with mechanical warm air furnace systems, 397
selection of, 381
sizes, 381, 389
temperature, 401
velocity through, 401
Reheater, 424, 432
Relative humidity, 9, 826
apparatus sensitive to, 684
in comfort zone, 64, 68
relation of dew-point to, 9
control of, 684
in industrial plants, 622, 624
for processing, 622
in public buildings, 67
in residences, 403
from water pans, 403
Relays, 685
Relief valves, 350
Repulsion motors, 706, 707
Research residence, 388, 406
Residences,
air distribution in, 397
automatic fuel burning equipment, 201
conditioning units, 291, 460
control systems, 399, 699
gas heat, 221
humidification of, 403
oil burners for, 213
requirements in, 405
steam consumption, 234
stokers for, 204
Resistance,
of bright metallic surfaces, 94
of building materials, 97
in ducts, 565, 643
of exhaust systems, 643
of niters, 396
of insulators, 97
thermal, 829
thermometer, 810
Resistor, 742
Respiratory diseases, 607
Restaurants,
tobacco smoke, in, 70
water supply to, 804
Return,
dry, 823
mains, 827
pipe, capacity, 308
Reverse cycle of refrigeration, 495, 749
Reversed return system, 332
Reynolds number, 184
Ringelmann chart, 816
Rock wool insulation, 100, 729
Roof, roofs, f ««,
coefficients of transmission of, 114
conductivities of, 101
solar radiation on, 152, 153, 154
ventilator, 672, 827
Room absorption correction charts, 557
Room control, 687
S
Salts in cooling water, 509
Saturated air, 827
Saturation, fiber point, 651
Scale,
in boilers, 260
Centigrade, 809
on equipment, 509
Fahrenheit, 809
in pipe, 374
Reaumur, 809
School, schools,
air flow necessary in, 70
optimum air conditions, 65
stokers suitable for, 201
temperature of, in winter, 134
ventilation in, 70
Scrubbers, 499, 528
Self-contained control system, 686
Sensible heat, 147, 827
of air, 12
loss, 73
of water, 31
Series wound motor, 703
Service connections, 770
Sheet metal, for ducts, 580, 641
Shingles air leakage through, 123
Shunt wound motor, 703
Skin diseases, 607
Silica gel
with oxygen chambers, 606
regain of moisture of, 626
silicon dioxide, 41
equilibrium conditions, 43
system of adsorption, 39, 41, 491
Single phase motor, 706
Sizes of pipe, (see Pipe Sizes)
Skylights, 117, 671
Sling psychrometer, 814
Slip-ring wound motors, 710
Smoke, 79, 827
abatement of, 84
measurement of, 816
recorders, 816
tobacco, 70
Smokeless arch, 828
Solar heat, 151
absorption coefficients, 155
effect of,
awnings, 155
latitude, 152
intensity chart, 150
occlusion of, 84
radiation,
factors, 154
through glass, 152
through walls. 152
time lag, 155
Solenoid valves, 685
Sound, 583, (see also Noise)
absorption coefficients, 589
control, 583
duct lining factor, 593
effect on duct design, 567
insulation of, 589
intensity, 335
measurement of, 584
in steam heating systems, 303
unit of, 583
Specific density, 3
Specific gravity, 2, 828
of fuel gas, 176
Specific heat, 3, 828
of air, 5
mean, of water vapor, 3
of water, 31
• Specific humidity, 8
Specific volume, 3, 828
of saturated steam, 31
Split phase motor, 707
Split system, 828
air conditioning equipment, 461
automatic control of, 689
central fan, 409
unit ventilators, 445
Pbooths for painting, 640
wiuls. 513
efficiency of, 512
towers, 514
distribution of, 504
generation of, 504
humidifiers, 505
type of central station system, 423
water coolers, 482, 512
Square foot of heating surface, 828
Squirrel cage motors, 707
Stack, stacks, 378, 689
effect, 670
* 675
wall, 380
Stairways, 129
HEATING VENTHJITING AIR CONDITIONING GUIDE 1938
Standards,
air, 82fe
air conditioning, 51
A.S.H.V.E. codes and standards, 248, 271, 839
for fuel oil, 173
for pipe, 350
for radiators. 271
for welding, 368
Static pressure, 828
Steam, 828
coils, 452
condensing rates, 266
consumption for buildings, 234
flow, Babcock's formula, 502
heat content of, 23
heating systems, 275, 828
air-vent, 276, 270. 309, 310
atmospheric, 283, 313, 321
classification, 275
condensation return pumps, 292
connections, (see Connections, Fittings)
corrosion of, 374
design of, 275, 301
dirt pockets, 328
district heating, 765
dripping of, 327
electric, 745
equivalent length of run. 305
gravity systems, 275
one-pipe, 275, 270, 309, 321
two-pipe, 279, 310, 321
with high-pressure steam, 313
mechanical, 275
orifice, 200, 303, 313, 321
pipe, 301. (set also Pip*)
sizes,*
pressure drop in. 278
sub-atmospheric, 287, 293, 303, 313, 321
types of, 275
vacuum, 285, 293, 295, 312, 830
vapor, 303, 321, 830
one-pipe, 280, 826
two-pipe, 281, 282, 311, 829
water hammer in, 303
zone control, 291
high pressure, 313
jet apparatus, 477
meters for, 774
pressure, 313
properties of, 28
requirements of buildings, 234, 777
saturated, properties of, 31
savings in use of, 770
superheated, 265, 828
trap, 828
tunnels, 769
underground, 767
in unit heaters, 440
Sterilization of air, 600
Stokers,
apartment house, 206
automatic control of. 399, 699
classes of , 204
combustion process, 209
adjustments. 212
efficiency, 212
commercial, 206. 208
controls, 213
design of, 201
economy, 201
household, 204
mechanical, 201
operating requirements, 205
overfeed flat grate, 201
overfeed inclined grate, 202
heating boilers, setting heights, 211
types of, 201
underfeed, 201, 829
underfeed rear cleaning, 203
underfeed side cleaning, 202
of hoi water, 798, SQ2
temperatures and humidities for,622
Storm sash, 125
Streptococcus, 52
Stroke, heat, 599
Sub-atmospheric systems, (see also Steam Healing
Systems)
Suction,
static in exhaust systems, 635
Summer,
care of heating boilers, 261
comfort zone, 64, 66
conditioning, apparatus for, 423, 451, 499
desirable indoor conditions in, 66
wind velocities and directions, 148
Sun,
effect on heating requirements, 291
factor of cooling load, 151
Supply outlets,
selection of, 381
types of, 389
Surface,
conductance, 828
cooling, 431
equipment, 431
air conditioning, 423
ratings, 429
extended, gravity-indirect heating systems, 272
heating, 829
square foot of, 828
radiant heating, 759
Sweating of pipe, 734
Swimming pool, 804
Symbols,
for drawings, 836
for heat transmission formulae, 90
Synchronous motor, 711
Synthetic air chart, 829
Systems of control, 686
Tank, tanks,
for domestic water supply, 798, 802
expansion, 349
flush, 790
Tees, dimensions of, 367
Temperature,
absolute. 819
of air leaving outlets, 428, 549
apparatus sensitive to, 684, 819
atmospheric, 184
of barns, 697
base, for degree-day, 231, 234, 235
basic, 3
body, 53, 54. 754
changes, effect on human beings, 55
of chimney gases 184
in cities, 138, 148, 232
of city water main, maximum, 508
control of, 213, 220, 225, 684, 750
railway air conditioning, 613
of cooling water, 482
dew-point, 3, 822
difference,
between floor and ceiling, 136, 226, 439
desired, determination of, 674
in stacks and leaders. 378. 673
dry-bulb, 2, 68, 823
maximum design, 148
specified in winter, 134
for drying, 652
effect on moisture regain, 622
effective, 58, 68, 135, 147, 823
chart, 58, 60, 61, 62, 64
for maximum comfort, 64, 756
optimum, 62
scale, 59
of gas flame, 176
in industrial ]
I processing, 722, 723
inside, 63. 64, 134, 412
surfaces, 758
low, insulation for, 723
of mean ulterior surface, 758
ALPHABETICAL INDEX TO TECHNICAL DATA SECTION
Temperature (continued)
mean radiant, 754, 758
measurement of, 679, 683, 809
in occupied space, 68
outside, 136, 148
radiation-convection, 762
range of cooling equipment, 511
records of cities, 138, 148
at registers, 428, 649
room, 10, 231, 820
sensations, 57
surface,
of man, 755
mean interior, 758
systems for control of, 213, 220, 225, 684, 750
thermo-equivalent conditions, 59
•water main, maximum, 508
of well water, 506
wet-bulb, 11, 814, 830
average, 511
design, 147, 511
as index of air distribution, 72
maximum, 511
Terminology, 819
Test codes, 248
Test instruments, 807
Test methods, 807
Textile, textiles,
fibers, regain of moisture, 621
temperatures and humidities for processing, 623
Theaters, temperatures of, 67, 134
Therm, 829
Thermal resistance, 829
Thermal resistivity, 829
Thermocouples, 807
Thermodynamics, 829
of air conditioning, 1
laws of, 826
Thermo-equivalent conditions, 59
Thermometer, 809, 810, 811
Thermocouple, 809
Thermopile, 810
Thermostat, thermostats, 684, 829
differential, 10, 683
with gas-fired furnaces, 225
immersion, 684
insersion, 684
location of, 399
with oil burners, 220
pilot, 690
with radiant heaters, 750
room, 684
surface, 684
types of, 673, 684
Time lag, 155
Tobacco smoke, 70
Ton of refrigeration, 475, 829
Ton-day of refrigeration, 829
Total heat, 829
Total pressure, 829
Towers, cooling, 482, 512, 514, 515
return, automatic, 298, 299
with steam heating systems, 281, 295
types of, 295
Tube,
Bourdon, 808
Pitot, 811
shell and tube heat exchanger, 483
Tuberculosis, 83, 608
Tubing, copper or brass, 365
Tunnels, for steam pipe, 769
Turbines, with unit heaters, 444
Two-pipe steam heating systems, (see also Steam
Heating Systems)
Two position controls, 686
Typhosus, 52
Ultra-violet light, 75, 84
Underfeed distribution system, 829
Underfeed stoker, 229
Underground piping, 767
Underwriters' loop, 276, 318
Unit air conditioners, 435, 451, 829
air distribution, 455
classification, 436
controls for, 466
cooling, 453
dehumidification, 453
filtering, 454
heating, 452
humidifying, 452
location of, 455
residential, 460
types of, 436, 456
Unit coolers, 435, 449
control of, 695
design of, 450
frost removal from, 450
Unit equipment, 435
advantages, 435
controls, 694
miscellaneous, 464
Unit heaters, 435, 744, 829
air temperatures, 439
control of, 695
direction of discharge, 441
piping connections, 442
ratings of, 441
Unit ventilators, 435, 444, 445, 446, 447, 829
control of, 696, 830
Unwin pressure drop formula, 766
Up-feed piping systems, 275, 830, (see also Steam
Heating Systems)
Vacuum gage, 808
Vacuum pumps, 292
Vacuum refrigeration, 477
control of, 701
Vacuum system of steam heating, (see also Steam
Heating Systems)
Valve, valves, 370
apparatus which operates, 683
on boilers, 258, 316
connections for, 770
control, 685
with steam heating systems, 315, 370
with high pressure steam, 313
pressure-reducing, 314, 770
ratings of, 313
for radiators, 277, 581
relief, 350
roughing-in dimensions, 373
solenoid, 685
sub-atmospheric system, 587
on traps, 596
types of, 370
for water supply, 788
Velocity, 830
81 m ducts of buildings, 401, 569, 579
in exhaust systems, 635, 642
through heating units, 411
measurement of, 811
*i openings, 698
sU towers, 515
sound effect of, 579
chimney gas, 187
draft loss, 192
contours, 637
in ducts, 401, 635, 642, 811
of fans, 539
head, of fluids, 563
meter, 813
steam,
through an orifice. 313
in underground pipes. 765
water, in pipes, 336, 338, 339
wind,
choosing, 126
measurement of, 678
on natural draft equipment, 515
in natural ventilation, 669
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
\Vnt, vents,
on traps, 2$C
in unit ventilators, 446
Ventilation, 51, 609, 830, (see also Air Dis-
tribution)
of barns, 679
in drying, Ml
of Ranges, 680
in hospitals, 598, 902
mechanical, 77
with roof ventilators, 672
natural, 77
air changes per hour, 127
control of, 073
general rules for, 677
heat to be removed by. 675
openings,
doors, *57I
formula to determine size of, 009
location of, 675
skylights, 671
types of, 670
windows, 671
for public buildings, 70, 575
purpose of, 675
quantity of air necessary for, 70
railway air conditioning, 609
by registers, 673
for schools, 70
by stacks, 670, 673
symbols, 836
Ventilator, ventilators,
resistance of, 672
roof. 672, 827
unit, 235, (see also Unit Ventilators}
Venturi chimney, 180
Vibration of machine mountings, 587
Vitiation of air, 51
Volume,
of air and saturated vapor, 12
conversion equations, 834
furnace, 824
specific, 3
of saturated steam, 28
of water, 27
W-Z
Wall, walls.
absorption of heat. 155
ah- leakage through, 122
of chimneys, 195
condensation onr 141
fire, 640
heat transmission coefficients for, 89. 90, 97, 104,
106, 108
radiators, output, 264
solar radiation on, 152, 153
time lag through, 155
Warm air heating systems, 830
gas-fired furnaces for, 222
gravity, 377
mechanical, 393
Washers, air, 396, 49ft, 524, 525, 820
Water,
boiling point of, 27
circulating, temperature of, 512. 724
from city main*, 482, 508
cooling,
eojoipment, 507
quantity. 509
temperature, 606, 508
composition of , 27
demand, 785, 804
density of, 27
domestic supply, 783, 797
evaporation of. 516
factor of usage, 785, 804
flow from fixtures, 784, 785
freezing, 733
friction losses through pipes, 791
hammer, 303
heaters, 411, 799
heating, 783
Water (continued)
hot,
domestic supply, 783, 797
boilers, 799
demand for, 803
electric heating of, 747
pipe sizes for, 798
storage of, 798, 802
heating systems, 331, (see also Hot Water Heat-
ing Systems')
indies of water, 825
line,
in boilers, 258, 259, 275
in water supply systems, 790
make-up, 516
meters, disc, 789
pans, for humidification, 403
pipe, 787
pressures, 27
probable usage, 785, 804
properties of, 27
as a refrigerant, 37, 45
replacement of, 516
supply piping, 783
down-feed systems, 786
mains, 790
up-feed systems, 788
temperature, maximum main, 508
from wells, 506
thermal properties of, 27
vapor, 5, 10, 12
given off in combustion of gas, 175
heat content, 12, 23
mean specific heat of, 3
weight of saturated, 12
Weatherstripping, 126
Weight,
of air, 6
conversion equations, 834
of steam, 28
of vapor, 12
of water, 27
Welding, 355, 366
neck flanges, 371, 372
Well water refrigeration control of, 702
Well water temperature, 506
WeUbulb temperature, (see Temperature, Wet-bulb)
Wet return, 830
Wind,
in cities, 138, 148
effect on heating requirements, 137
forces in natural ventilation, 121, 669, 675
prevailing, direction of, 127, 148
records of velocity and direction, 138, 148
velocity on natural draft equipment, 515
average, 127, 137, 148, 669
equivalent, hi tall buildings, 128
used in calculations, 127
Window, windows, 671, 673
air leakage through, 124, 126
clearance of sash, 125
coefficients of transmission of, 117
comparison of various shades for, 156
crack, 124
measurement of, 124
solar radiation through, 152
storm sash, 125
Winter,
comfort zone, 63, 64
conditioning, apparatus for, 393, 409
cooling in, 147
humidification in, 63, 68, 403
inside temperature, 134
relative humidity in, 68
temperatures, 138
wind velocities and directions, 138
Zero, absolute, 819
Zone, zoning,
"for air conditioning systems, 428
automatic control, 688
comfort, 63, 64, 66, 821
control of steam heating systems, 291
for large heating systems, 351
neutral, 826
water supply systems, 783
HEATING VENTILATING
AIR CONDITIONING
Vol. 16 • v 1938
Chapter 1
AIR, WATER AND STEAM
Dalton's Law, Temperatures, Air Properties, Humidity, Rela-
tive Humidity, Specific Humidity, Relation of Dew Point to
Relative Humidity, Adiabatic Saturation of Air, Total Heat
and Heat Content, Enthalpy, Psychrometric Chart, Properties
o£ Water, Properties of Steam, Rate of Evaporation
A IR conditioning has for its objective the supplying and maintaining,
,/JL in a room or other enclosure, of an atmosphere having a composition,
temperature, humidity, and motion which will produce desired effects
ugon the occupants of the room or upon materials stored or handled in it.
Dry air is a mechanical mixture of gases composed, in percentage of
volume, as follows1: nitrogen 78.03, oxygen 20.99, argon 0.94, carbon
dioxide 0.03, and small amounts of hydrogen and other gases.
- j ^Atmospheric air at sea level is given in percentage by volume as: N2
77.08, O2 20.75, water vapor 1.2, A 0.93, C02 0.03 and H? 0.01. The
amount of water vapor varies greatly under different conditions and is
frequently one of the most important constituents since it affects bodily
comfort and greatly affects all kinds of hygroscopic materials.
DALTON'S LAW
A mixture of dry gases and water vapor, such as atmospheric air, obeys
Dalton's Law of Partial Pressures; each gas or vapor in a mixture, at a
given temperature, contributes to the observed pressure the same amount
that it would have exerted by itself at the same temperature had no other
gas or vapor been present. If p = the observed pressure of the mixture
international Critical Tables.
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
and pi, fa, pt, etc. = the pressure of the gases or vapors corresponding to
the observed temperature, then
P-#i + fc + />a, etc. (1)
TEMPERATURES
Air is said to be saturated at a given temperature when the water vapor
mixed with the air is in the dry saturated condition or, what is the equiva-
lent, when the space occupied by the mixture holds the maximum pos-
sible weight of water vapor at that temperature. If the water vapor
mixed with the dry air is superheated, i.e., if its temperature is above the
temperature of saturation for the actual water vapor partial pressure, the
air is not saturated.
The starting point of most applications of thermodynamic principles to
air conditioning problems is the experimental determination of the dry-
bulb and wet-bulb temperatures, and sometimes the barometric pressure.
The dry-bulb temperature of the air is the temperature indicated by any
type of thermometer not affected by the water vapor content or relative
humidity of the air. The wet-bulb temperature is determined by a thermo-
meter with its bulb encased in a fine mesh fabric bag moistened with clean
water and whirled through the air until the thermometer assumes a
steady temperature. This steady temperature is the result of a dynamic
equilibrium between the rate at which heat is transferred from the air to
the water on the bulb and the rate at which this heat is utilized in evapora-
ting moisture from the bulb. The rate at which heat is transferred from
the air to the water is substantially proportional to the wet-bulb depres-
sion (t — /l), while the rate of heat utilization in evaporation is propor-
tional to the difference between the saturation pressure of the water at
the wet-bulb temperature and the actual partial pressure of the water
vapor in the air (e} — e). Carrier's equation for this dynamic equilibrium
is
1-c B -j
t - /' 2800 - 1.3*'
In the form commonly used,
where
e — actual partial pressure of water vapor in the air, inches of mercury.
c1 = saturation pressure at wet-bulb temperature, inches of mercury.
B = barometric pressure, inches of mercury.
/ = dry-bulb temperature, degrees Fahrenheit.
t* = wet-bulb temperature, degrees Fahrenheit.
Formula 2b may be used to determine the actual partial pressure of the
water vapor in a dry air-water vapor mixture. Then, from Dalton's Law
of Partial Pressures, Equation 1, it follows that the partial pressure of the
dry air is (B - e).
If a mixture of dry air and water vapor, initially unsaturated, be cooled
CHAPTER 1. AIR, WATER AND STEAM
at constant pressure, the temperature at which condensation of the water
vapor begins is called the dew-point temperature. Clearly the dew-point
is the saturation temperature corresponding to the actual partial pressure,
e, of the water vapor in the mixture.
AIR PROPERTIES
Density is variously defined as the mass per unit of volume, the weight
per unit of volume, or the ratio of the mass, or weight, of a given volume
of a substance to the mass, or weight, of an equal volume of some other
substance such as water or air under standard conditions of temperature
and pressure. The term specific gravity is more commonly used to express
the latter relation but, when the gram is taken as the unit of mass and the
cubic centimeter as the unit of volume, density and specific gravity have
the same meaning. The term specific density is sometimes used to dis-
tinguish the weight in pounds per cubic foot; and as here used, density is
the weight in pounds of one cubic foot of a substance.
The density of air decreases with increase in temperature when under
constant pressure. The density of dry air at 70 F and under standard
atmospheric pressure (29.921 in. of Hg) is approximately 0.075 Ib (see
Table 1), while that of a mixture of air and saturated water vapor at the
same temperature and barometric pressure is only about 0.0742 Ib. In
the mixture the density of the dry air is 0.07307 and that of the vapor is
0.00115 Ib (see Table 2).
In order to make comparisons of air volumes or velocities it is necessary
to reduce the observations to a common pressure and temperature basis.
The basic pressure is usually taken as 29.921 in. of Hg, but no basic tem-
perature is universally recognized. Common temperatures for this
purpose are 32 F, 60 F, 68 F, and 70 F. Since 70 F is the most commonly
specified temperature to which rooms for human occupancy must be
heated, it is usually understood, when no other temperature is specified,
that 70 F is the basic temperature for measuring the volume or the
velocity of air in heating and ventilating work.
The specific volume of air is the volume in cubic feet occupied by one
pound of the air. Under constant pressure the specific volume varies
inversely as the density and directly as the absolute temperature.
The specific heat of air is the number of Btu required to raise the tem-
perature of 1 Ib of air 1 F. Distinction should always be made between
the instantaneous specific heat at any existent temperature and the mean
specific heat, which is the average specific heat through a given tempera-
ture range. The mean specific heat is the value required in most calcu-
lations. The specific heats at constant pressure, Cp, and the specific
heats, Cv, at constant volume are different. The specific heat at constant
pressure is commonly used and it varies, under a pressure of one atmos-
phere, from a minimum at 32 F from which it increases with either increase
or decrease of temperature. The value of 0.24, as the mean specific heat
at constant pressure, is sufficiently accurate for use at ordinary tem-
peratures. Values for instantaneous and mean specific heats are given
in Table 3.
The mean specific heat of 'water vapor at cqnstant pressure is taken as
0.45 for all general engineering computations.
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 1. PROPERTIES OF DRY AiRa
Barometric Pressure 29.921 In. of Hg
TaMWRATTRE WEIGHT POUNDS
DIG F PBB Cc FT
i
RATIO OF
VOLUME TO
VOLTME AT 70 F
BTTJ ABSORBED BY
ONE CTT FT DRY
Am PEE DEQ F
Cu FT DRY
AIR WARMED
ONE DEG
PER BTTJ
0
0.08633
0.8678
0.02077
48.15
10
0.08449
0.8867
0.02030
49.26
20
0.08273
0.9056
0.01986
50.35
30 0.08104
0.9245
0.01944
51.44
40
0.07942
0.9433
0.01905
52.49
50
0.07785
0.9624
0.01868
53.36
60
0.07636
0.9811
0.01832
54.44
70
0.07492
1.0000
0.01798
55.62
80
0,07353
1.0189
0.01765
56.66
90
0.07219
1.0378
0.01733
57.70
100
0.07090
1.0567
0.01702
58.75
110
0.06966
1.0755
0.01672
59.81
120
0.06845
1.0946
0.01643
60.86
130
0.06729
1.1133
0.01616
61.88
140
0.06617
1.1322
0.01589
62.93
150
0.06509
1.1510
0.01563
63.98
160
0.06403
1.1701
0.01538
65.02
180
0.06203
1.2078
0.01490
67.11
200
0.06015
1.2456
0.01446
69.24
220
0.05838
1.2832
0.01403
71.27
240
0.05671
1.3211
0.01364
73.31
260
0.05514
1.3587
0.01326
75.41
280
0.05365
1.3965
0.01291
77.46
300
0.05223
1.4344
0.01257
79.55
350
0.04901
1.5287
0.01181
84.67
400
0.04615
1.6234
0.01114
89.67
450
0.04362
1.7176
0.01054
94.87
500
0.04135
1.8119
0.01001
99.01
550
0.03930
1.9064
0.00953
104.93
600
0.03744
2.0011
0.00908
110.13
700
0.03422
2.1893
0.00833
120.05
800
0.03150
2.3784
0.00769
130.04
900
0.02911
2.5737
0.00713
140.25
1000
0.02718
2.7564
0.00668
149.70
H> Sev5M- b38ed on the instantaneous specific heats of air.
CHAPTER 1. AIR, WATER AND STEAM
TABLE 2. PROPERTIES OF SATURATED AiRa
Weights of Air, Vapor and Saturated Mixture of Air and Vapor at 29.921 In. of Hg
TEMP.
DsoF
WEIGHT IN A CUBIC FOOT OP MEKTUBE
BTU
ABSORBED
BY ONE
CUBIC
FOOT
SAT. Am
PER DEO F
CUBIC
FEET
SAT. Am
WARMED
ONE DEO
PEE BTU
SPECIFIC
HEAT BTU
PER POUND
OP
MIXTURE
Weight of
Dry Air
Pounds
Weight of
Vapor
Pounds
Total Weight
ofMirture
Pounds
0
0.08622
0.000068
0.08629
0.02078
48.12
0.2408
10
0.08431
0.000111
0.08442
0.02031
49.24
0.2406
20
0.08244
0.000177
0.08262
0.01987
50.33
0.2405
30
0.08060
0.000278
0.08088
0.01946
51.39
0.2406
40
0.07876
0.000409
0.07917
0.01908
52.41
0.2410
50
0.07692
0.000587
0.07751
0.01872
53.42
0.2415
60
0.07503
0.000828
0.07586
0.01838
54.41
0.2423
70
0.07307
0.001151
0.07422
0.01805
55.40
0.2432
80
0.07099
0.001578
0.07257
0.01775
56.34
0.2446
90
0.06877
0.002134
0.07090
0.01747
57.24
0.2464
100
0.06634
0.002851
0.06919
0.01721
58.11
0.2487
110
0.06361
0.003762
0.06737
0.01696
58.96
0.2517
120
0,06057
0.004912
0.06548
0.01675
59.70
0.2558
130
0.05712
0.006344
0.06346
0.01657
60.35
0.2611
140
0.05317
0.008116
0.06129
0.01642
60.91
0.2679
150
0.04863
0.010284
0.05891
0.01630
61.35
0.2767
160
0.04339
0.012919
0.05631
0.01624
61.58
0.2884
170
0.03733
0.016092
0.05342
0.01621
61.69
0.3034
180
0.03033
0.019888
0.05022
0.01624
61.58
0.3234
190
0.02228
0.024384
0.04666
0.01633
61.24
0.3500
200
0.01298
0.029700
0.04268
0.01649
60.64
0.3864
210
0.00230
0.035932
0.03616
0.01672
59.81
0.4624
212
0.00000
0.037286
0.03729
0.01818
55.01
0.4875
^Compiled by W. H. Severns, based on the instantaneous specific heats of air.
TABLE 3. SPECIFIC HEATS OF DRY AiRa
Constant Barometric Pressure of 29.921 In. of Hg
TEMPERATURE
DE0F
INSTANTANEOUS
OSTBUB
SPECIFIC HEAT
TEMPERATUBE
RANGE
DBGF
MEAN
SPECIFIC
HEAT
-301.0
0.2520
32 to 212
0.2401
-108.4
0.2430
32 to 392
0.2411
32.0
0.2399
32 to 752
0.2420
212.0
0.2403
32 to 1112
0.2430
392.0
0.2413
752.0
0.2430
1112.0
0.2470
•Compiled by W. H. Severna, based on data given in the International Critical Tables.
5
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
', -* ^ ^ ,H fs, r* ,>, r
-^
000 000 000 OOP
rf« -*1 «"O f*5 ?O c-1 cs •»— i *H *— i »-H O
o
H
S
a
2
I
I
o |
g 0
1*
Is
«sa:
jo* do odd dod ddo* odd o'o'd POP
f o* cc oo" " "r-^r^o o~o~o ~r;;ro6~ci' O~CN"^ o oTco \o oo •»-
! j? 5, J2 jddd odd odd odd OOP" P'P'O PPP
~O~ CM' ""
es
!ooq qoq qqq S8q qqq qqS
I o* o* d ooo odd odd odd odd PPP
>C CC CN CM T-l TH T-H TH O
OOO OOO OO'O 000 000 OOO" OOO
I ooo coo OPO odd ooo" odd POP
§
o
ooo o o" d d o* o* odd odd odd
ooo ooo ooo odd odd odd odd
IMS*
odd do'd
"O~vCTvO NO 10 10
8±$
«!
gfci
6
uiG
§§3 _
ooo odd odd odd odd. odd odd
Ri
h w co co CM
4 CN "*H r-1 TH p
3£J£3 cs
odd odd odd odd ddo
ooo ddo*
IO to >O vOvOt*- 00 O\ *H
d o* d PPP ddd
oopvo **» co cs
OOCN»0 0\^S
t^vO-^ <N TH O\
f**t*>t>- r*-t^\o
qqq qqq
odd odd
) UO 00 T-I V
ooo PPP
PT) CS CN OO OO O CM CS CO
odd PPP* ddd
BSS
SSS SSS
PPP PPP
3iO »O
H CO COCOCM CM CS TH »H ^H C
ooo ooo ooo ooo ood
odd o'o'd
PPP ooo POP ppp PPP odd odd
88 III
^ss sss
ooo odd
sis sss ssi
odd odd ddo"
S.2.3. S8S
POP odd
oo<
o 005
5
11
s 5
•85
J5
II
IJ
i
1 5*
I
Hi
CHAPTER 1. AIR, WATER AND STEAM
Table 4 is intended to aid in determining the density of moist air,
taking into account its temperature, pressure, and moisture content.
Example 1. To show the use of Table 4: Given air at 83 F dry-bulb and 68 F wet-
bulb (or a depression of 15 deg) with a barometric pressure of 29.40 in. of mercury.
What will be the weight of this air in pounds per cubic foot?
Solution. From Table 4 the weight of saturated air at 80 F and 29.00 in. barometer is
found to be 0.07034 Ib per cubic foot. There is a decrease of 0.00015 Ib per degree dry-
bulb temperature above 80 F. There is an increase of 0.00025 Ib for each 0.1 in. above
29.00 in. From the last column of Table 4 it is found that there is an increase of approxi-
mately 0.000035 Ib per degree wet-bulb depression when the dry-bulb is 83 F. Tabu-
lating the items:
0.07034 = weight of saturated air at 80 F and 29.00 bar.
- 0.00045 « decrement for 3 deg dry-bulb, 3 X 0.00015.
+ 0.00100 = increment for 0.4 in. bar., 4 X 0.00025.
+ 0.00053 = increment for 15 deg wet-bulb depression, 15 X 0.000035.
0.07142 = weight in pounds per cubic foot of air at 83 F dry-bulb, 68 F wet-bulb,
29.40 in. bar.
It is usual to assume that dry air, moist air, and the water vapor in the
air follow the laws of perfect gases. This assumption while not absolutely
true, especially with saturated vapor at temperatures much above 140 F,
is sufficiently accurate for practical purposes and it greatly simplifies
computations.
Boyle's Law refers to the relation between the pressure and volume of a
gas, and may be stated as follows : With temperature constant, the volume of
a given weight of gas varies inversely as its absolute pressure. Hence, if
PI and P2 represent the initial and final absolute pressures, and V\ and
F2 represent corresponding volumes of the same mass, say one pound of
•FT -p
gas, then^~ = -=2, or Pi Vi = P2 F2, but since Pi 7i for any given case is
V2 Jri
a definite constant quantity, it follows that the product of the absolute
pressure and volume of a gas is a constant, or PV = C, when T is kept
constant. Any change in the pressure and volume of a gas at constant
temperature is called an isothermal change.
Charles1 Law refers to the relation among pressure, volume, and tem-
perature of a gas and may be stated as follows : The volume of a given
weight of gas varies directly as the absolute temperature at constant pressure,
and the pressure varies directly as the absolute temperature at constant
volume. Hence, when heat is added at constant volume, Fc, the resulting
•p *p
equation is ^ = -=r, or, for the same temperature range at constant pres-
"\ -LI
Vz T*
sure, PC, the relation is « = TF-
1/1/1
In general, for any weight of gas, T7, since volume is proportional to
weight, the relation among P, F, and T is
PV = WRT (3)
where
P «= the absolute pressure of the gas, pounds per square foot.
V = the volume of the weight W, cubic feet.
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
W = the weight of the gas, pounds. »
R * a constant depending on the nature of the gas. The average value of R for air
is 53.34.
T « the absolute temperature, degrees Fahrenheit.
This is the characteristic equation for a perfect gas, and while no gases
are perfect in this sense, they conform so nearly that Equation 3 will
apply to most engineering computations.
HUMIDITY
Humidity is the water vapor mixed with dry air in the atmosphere.
Absolute humidity has a multiplicity of meanings, but usually the term
refers to the weight of water vapor per unit volume of space occupied,
expressed in grains or pounds per cubic foot. With this meaning, absolute
humidity is nothing but the actual density of the water vapor in the
mixture and might better be so called. A study of Keenan's Steam
Tables2 indicates that water vapor, either saturated or super-heated,^ at
partial pressures lower than 4 in. of mercury may be treated as a gas with
a gas constant R of 1.21 in the characteristic equation of the gas pV —
wR (t + 460). Within such limits, the density (d) of water vapor is
1.2! (-f 460)
5785 e
(Pounds *** cubic foot)
460
(grains per cubic foot) (4b)
where
e — actual partial pressure of vapor, inches of mercury.
t — dry-bulb temperature, degrees Fahrenheit.
Specific Humidity
It simplifies many problems which deal with mixtures of dry air and
water vapor to express the weight or the mass of the vapor in terms of the
weight or the mass of dry air. If the weight of the water vapor in a
mixture be divided by the weight of the dry air, and the weight of dry air
be made unity, we have an expression of the weight of water vapor carried
by a unit weight of dry air. This relation has no generally accepted name.
It has been variously called: mixing ratio, proportionate humidity, mass
or density ratio, absolute humidity, and specific humidity. Of all these
terms specific humidity is the most suggestive of the meaning which it is
desired to express and it has found considerable use in this sense even
though it is defined in International Critical Tables as the ratio of the
mass of vapor to the total mass. It will be understood here that specific
humidity refers to the weight of water vapor carried by one pound of
dry air.
The gas constant for dry air, when the partial pressure of the air is
expressed in inches of Hg, is 0.753; so that the specific humidity, if
represented by W, is
"Published by American Society of Mechanical Engineers, see abstract in Table 8.
8
CHAPTER 1. AIR, WATER AND STEAM
W -
B-e
1.21 (t + 460)
= 0.622 -
0.753 (t + 460)
(pounds)
(5a)
(5b)
-4354 (£) (grains)
where
e = actual partial pressure of vapor, inches of mercury.
B = total pressure of mixture (barometric pressure), inches of mercury.
Relative Humidity
Relative humidity ($) is either the ratio of the actual partial pressure,
e, of the water vapor in the air to the saturation pressure, et, at the dry-
bulb temperature, or the ratio of the actual density, d, of the vapor to
the density of saturated vapor, dt, at the dry-bulb temperature. That is:
The relative humidity of a given mixture at a.giyen temperature is not
the same as the specific humidity, W, of the mixture divided by the
specific humidity, Wt, of saturated vapor at the same temperature, for
from Equations 5a and 6
Wt - °-622
0.622
(-=*-)
\ B-et )
B —
(7)
The specific humidity of an unsaturated air-vapor mixture cannot,
therefore, be accurately found by multiplying the specific humidity of
saturated vapor by its relative humidity; although the error is usually
small especially when the relative humidity is high.
With a relative humidity of 100 per cent, the dry-bulb, wet-bulb, and
dew-point temperatures are equal. With a relative humidity less than
100 per cent, the dry-bulb exceeds the wet-bulb, and the wet-bulb exceeds
the dew-point temperature.
RELATION OF DEW POINT TO RELATIVE HUMIDITY
A peculiar relationship exists between the dew-point and the relative
humidity and this is found most useful in air conditioning work. This
relationship is, that for a fixed relative humidity there is substantially a
constant difference between the dew-point and the dry-bulb temperature
over a considerable temperature range. Table 5, giving the dry-bulb and
dew-point temperatures and the dew-point differentials for 50 per cent
relative humidity, illustrates this relationship clearly.
TABLE 5. TEMPERATURES FOR 50 PER CENT RELATIVE HUMIDITY
Dry-bulb temperature..—... ..
65.0
70.0
75.0
80.0
85.0
90.0
Dew-point temperature.
45.8
50.5
55.25
59.75
64.25
68.75
Difference between dew-point and dry-
bulb temperature
19.2
19.5
19.75
20.25
20.75
21.25
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
It will be seen from an inspection of this table that the difference
between the dew-point temperature and the room temperature is approxi-
mately 20 deg throughout this range of dry-bulb temperatures or, to
be more exact, the differential increases only 10 per cent for a range of
practically 25 deg.
This principle holds true for other humidities and is due to the fact
that the pressure of the water vapor practically doubles for every 20 deg
through this range.
The approximate relative humidity for any difference between dew-
point and dry-bulb temperature may be expressed in per cent as:
100
2^ W
where
/I = dew-point temperature.
This principle is very useful in determining the available cooling effect
obtainable with saturated air when a desired relative humidity is to be
maintained in a room, even though there may be a wide variation in room
temperature. This problem is one which applies to certain industrial con-
ditions, such as those in cotton mills and tobacco factories, where re-
latively high humidities are carried and where one of the principal prob-
lems is to remove the heat generated by the machinery. It also permits
the use of a differential thermostat, responsive to both the room tempera-
ture and the dew-point temperature, to control the relative humidity
in the room.
Table 6 gives, for different temperatures, the density of saturated vaporr—
dt, the weight of saturated vapor mixed with 1 lb of dry air, Wt, (at a
relative humidity of 100 per cent and a barometric pressure, B, of 29.92 in.
of^mercury), the specific volume of dry air, and the volume of an air-vapor
mixture containing 1 Ib of dry air (at a relative humidity of 100 per cent
and a pressure of 29.92 in. of mercury). The preceding equations or the
data from Table 6 may be conveniently used in solving the following-
typical problems: 5
*& » to be maintained at 70 F with a relative
= 04) when the outside air is at 0 F and 70 per cent
a baro<netric Press^' *> of 29.92 in. of mercury Fmd
t0 *"* V*™* °f dry air and *** dew'P°int temperature
Solution. From Equation 5a and Table 6,
Wl = 0.622 (29.92-0.0264) " °-000548 lb P«r Pound of dry air.
W, - 0.622 ( 29.92X-° olfg ) = °'00618 lb *>* P°und of dry air.
An approximation of the same result from Table 6 is
Wk -• 0.4 X 0.01574 = 0.006296 lb per pound o?dry ai?
10
CHAPTER 1. AIR, WATER AND STEAM
The water vapor added per pound of dry air is approximately 0.00574636 Ib and the
dew-point temperature is approximately 45 F. The degree of approximation is evident.
Example 8. Dehumidifying and Cooling. Air with a dry-bulb temperature of 84 F,
a wet-bulb of 70 F, or a relative humidity of 50 per cent ($ = 0.5), and a barometric
pressure, B, of 29.92 in. of mercury is to be cooled to 54 F, Find the dew-point tem-
perature of the entering air and the weight of vapor condensed per pound of dry air.
Solution. From Equation 5a and Table 6,
wl - 0.622 - " °'01248 lb per pound of dry air*
°'622 " " °-00887 Ib Per P°Und
Since W\ — Wt when t — 63.4 F, this is the dew-point temperature of the entering air.
The weight of vapor condensed is (Wi — W^ or 0.00361 lb per pound of dry air.
An approximate result is
Wi - 0.5 X 0.02543 - 0.012715 lb per pound of dry air.
Wt = 1 X 0.008856 = 0.008856 lb per pound of dry air, since the exit air is saturated.
Since W\ — Wt at t — 64 F, this is the dew-point temperature of the entering air.
The weight of vapor condensed is 0.003859 lb per pound of dry air. The degree of approxi-
mation is again evident.
ADIABATIC SATURATION OF AIR
The process of adiabatic saturation of air is of considerable importance
in air conditioning. Suppose that 1 lb of dry air, initially unsaturated but
carrying W lb of water vapor with a dry-bulb temperature, /, and a wet-
bulb temperature, f, be made to pass through a tunnel containing an
exposed water surface. Further assume the tunnel to be completely in-
sulated, thermally, so that the only heat transfer possible is that between
the air and water. As the air passes over the water surface, it will gradu-
ally pick up water vapor and will approach saturation at the initial wet-
bulb temperature of the air, if the water be supplied at this wet-bulb tem-
perature. During the process of adiabatic saturation, then, the dry-bulb
temperature of the air drops to the wet-bulb temperature as a limit, the
wet-bulb temperature remains substantially constant, and the weight of
water vapor associated with each pound of dry air increases to Wv, as a
limit, where Wv is the weight of saturated vapor per pound of dry air for
saturation at the wet-bulb temperature.
Example 4- If air with a dry-bulb of 85 F and a wet-bulb of 70 F be saturated adia-
batically by spraying with recirculated water, what will be the final temperature and the
vapor content of the ah-?
Solution. The final temperature will be equal to the initial wet-bulb temperature or
70 F, and since the air is saturated at this temperature, from Table 6, W - 0.01574 lb
per pound of dry air.
In the adiabatic saturation process, since the heat given up by the dry
air and associated vapor in cooling to the wet-bulb temperature is utilized
in evaporation of water at the wet-bulb temperature, W» H. Carrier has
pointed out8 that the equation for the process of adiabatic saturation, and
hence for a process of constant wet-bulb temperature, is:
'Rational Psychrometric Formulae, by W. H. Carrier (A.S.M.E. Transactions, Vol. 33, 1911, p 1005.)
11
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
M
8 '
I IJN
S S3 IS 15 S
oooo ooooo ooooo
H iH iH r-l i-l ,-< ,-1 ,H tH T-l ^ »H »H iH iH
<M (N(N(NM(N
!!!! | I | I J I I I I I I I I 1 I I I I I I I I I I I I I I I I
OOi~l CCOCOr-IC
QiHCOCOOO i-t
0000060006 0606060606 0606060606 060600606 060000 0 000 os
iHeeooOT-i cooooi-ieo COOOTHCOCD OQIHCQCOOO i-HcoeooiH TPCDQIHTH oosi-t^co
OOCCCOW^ •^•^•^lOifl »CiO«O«OeO «Dt-t-t«-^ OOOOOOOOO CSOSOOO OO»HiHi-l
00000 00000 00000 00000 00000 0 06 06 cJ oi osoicooioj
I
I
IIP III
Soooo oooc
eo«4iiONo> ON-
no UDOCOO«O r-no^Ho
2S 2§5?S^§ g§2g
is sisls ssii
gsggg
sssss
I
3
o o""*'"o"""""o"
•s
c
NCOCQDS-^ Ttl^
o" o"
*i— I Or-nC-^HN
i 1 1 1 1 1 7 7 1 1 TTTTi i 1 77 1 77777 77777 71 ' ' '
12
CHAPTER 1. AIR, WATER AND STEAM
D
I
u
i— r
I
THO>iCOH5 iHOWN-OQ 00-^P^O OOO»-IN. NOOCC05W5 OOt-f^-CC r-MCS^O
Of«iocoo OO»COQOOO «ocooooco coF-ioooeo IHOOOCCH OO^T-IOS o^i-icsP
M M i M i ii MM? 77777 77777 77777 77777
Oi-HO O^OiCOOO
OCfio OOOSOS
SSSgS §S§
33383 8 S8SSS 22222 25555 SSSSSS SSS«
M M I M M I M M I M M I MM! M M I MM!
W
-BSJ
z$
•si
t tOOSr^^CO ON^b-OJ C^^*t-OSN •* N OS N •*
eOCQCOCQ^t ^i^l^JiOiO iSiOOCOO Ob-l>Nt^ 000000000 00000
OJC5CJCSC5 ciciacJoi cscJoicioi oodo'oi oioio'cicj cJcicioos oioioo'd
eoweoeo^j
CRC&OO5O5
O3O>0>0>0)
x^
s
<;
00000 OOOOC
3g §§§SS
ggS^ 2feS2S §g§?2 £§2fc2
«>>«!0 NWOOOO NuaoOrHlO OQ«C$TH«P
t^^osmt-i ocQ1^eo^
o^2c5c§ ^SSooo
ON OOCO"#t-O 00 tC
8SSS8
i-i *n co IH r*.
TjtCSiOi-Hb-
OikCt*-b-CO i-i<MiCT-liO CO >O OTIC1
o* o* o"
H^H OSOOOI>
tooao ino
s
BE
fi-<*CC(NiH OOOOt-CO iC-gCONiH OOOOt-CD kfl-^CONi
^OO5O>C5 9^00000000 00 00 00 00 00 OOlSt^C^t** C>S»t>»l>J
Mill I M I I I I I II Mill II I I
iC500t»-eo iftjgwNtH
MM I I I I I
•a
13
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
'53
-?0«5»-i??
Ot- <P«^M?i
5. s $§3§£R 5s2£S3 S3&38 «S8S§5 SSSSS 33883 S&SS8
6s"1" -2 '^W-* -r-**-.i-<{-.i -.,',_! ,H',_I,^ o'ddcJos doscsoooo oooot>b»i> b-cocooco
£=£ ^^^^2 y^J^^1 ^-<^^^ ^^-r^ i i i i i i i i i i i i i i i i
Ed
I
3
&&
9«-*
r°s
*2J
§|ll sis's's' s's'ss's" s'ssss sssss s'ssss sssss sssss
I
— • £* I QQSOO OC5OOO OG3C3OO OCSOOO OOOOO OOOOO OOOOO
v.j£j I SSSSS SSSSrH ^rtS^S S^THiHTH tHiHi-lrHiH ^r^iHrS^-l rH rH rH i-( i-l
R
"g i ^Ji^^S «N?IN« OJSOWOTW §^-**S wSooS t*ooooa
'£ id"""' o" c d d d
COCCCC^HlO
oco-*t^co
occwcoeo -*-
i ! ^
i,il
1
a
I
o o o o o o o
O
3
tt
ll
so v
Q M T* iH |> NOOOOW
--
OOOO
o»io£-«
OO>OOSC5 OC5O
eoeow^t^ CBcot
rt<tOOb>00 O'-H
MC4C4 C4C4COCQC
S§§8 SS
9^9 J3«
s
£
i
I
'o §®^^* I§^^^^J ®wc§D3W wwoiSco
Mill i i i f i i i i i i i i i i i i i i i i i i i i i TTTTT
14
CHAPTER 1. AIR, WATER AND STEAM
i
u
I
^
O
H-3
H
I
Q
H
H
C/}
"•SJ
53
«"sr""
f. ^ 00^
1C rH t» (M t>- rH-tf U500r^ t>00)OCO t>j O O i-i b- §§3^§* £•>
n
"i
= 3
MM Mill 1 1 1 1 1 IMIS 1 M -H+ +
1
O^OCOOO Clt-rHOO OO^OOfO !>CNOi-tiO O"tC5COCO W
1
1
^1
1
6
1
.g
S
1
-2
MM Mill MM! 1 1 1 1 1 M M 1
o
-So?
•sH
,Q.i
?^
Vapor to
Saturate it
t-l i-< iH T-l «H r-l r-l »-( i-l »-< i-l rH iH r-l rH r-l ?H r-l r-t r-4 r-H »-H rH r-< i-l tH
VOLUME i
BAROMETER, 1
t
-
<4
3 .ft
5 •<
3»
»Ot-OOJ»O t^OCO»OOO OCO^OOOO COiOOOOCC tS^SSS §
OOi-liHi-l T-tr-lr-lTHT-t i-ti-lr^i-l»H ^ '"I rl ^"1 ]^ Zlllllllr2!l3 2
^ ,H »-< TH r-l rH rH r-< i-H rH r-t iH r-( iH rH i-H rH »H rH »H r-l rH r-l i-t ri r-i
Q
J
O
Illil 11111 Ilili llill 1
1
•s
jQ
fi
OOOCO(NO lCr-nOCN*O TfOOOO1^ QOOO»OOO1 Sfeo§S S
e -
.S
illl IIIII IIIII Hill IIIII I
1
53
o
o " ' " ' o" " " ' " o * " * ' o" * * ' * o" o
0
fi
TH^NNW NWNNoi CO CO CO CO CO -*^^-*O iOo"iO«D« O
§
ss
OOOOO'O OOt-'OOOO t» ^1 lO iO rH CDOOOOCO U5 ?O SO CO *O CO
I-
I
illli sllSS lllSi ISill liiii i
'Jx
^
§«
s 2
W
<« o o o o o
M
rM
s
1
-4
^777 77777 77777 71 ' ' ' ' ' ' ' '
15
HEATING VENTILATING Am CONDITIONING GUIDE 1938
WNOJ101> COMCOOSCO
H '
Ez,
:iltl
«* 00 i-* CO ® OS »-l T*< t«» OS (M^OO
oooooseo ooooo »H»HIH
ac o M *c DO oro»cooo cooooi-^co oooococo OOT-HCOCDOO »-<eocooor-i co«ooo»-ieo
' SfflSSOO fc-fr-Nb-OO OOOOOOOO CSCSOOO OtH^rH»H <NCNJ(M(NCO CO CO CO Tfl Tt<
'' * " *
5O?*!*- NOOOCO 00>O»CCO
* r-i rf !>• T-n-'JOOCOl^ »-* O *H CO
'-uncCCOS- lOb-'tHC
Ol>»OCOiH OCSCSO
OiHN ^uOcDtOO
OC^t'-'H— i-itN.cqoo-*
i-HOiOCOO M CO 1C t- CO rt<Oi-iCO<Q <MCO*-tCOCO 0> i-H i-H r-i T*
>-i )> id (N O CO CO »O ** -* ^ UO CO 1> OS <M »O Oi CO 00 COOt-OOOS
!E! I ii§S8S Si
c^
u*
c
I -" ' r-(C5!?3
III « 13!
b-2
O(M OrJHO^O (M (N O Tt* >O
-•*iHflj
tllOCOCO
1>THO51OCO »OOOlM»Ot^
T^COCOCOr^ ii5N-T^"^Ol
I>iOrhMlN NCMCO^lO
b«OOO5OrH - iMOQTfllOO
i
i-l NiHXOi-i COOO50CM OiOOOrH
-
iiS
ssiss.
5D I J>t^OOO-* OO^r-IOSOO C35r-(«OOl> CD CO O5 CO OS OOOONCO-* rH CO C
£3 jr-CJrHTT'CO OOi— I«*COCS N CO O5 CO CO O ^ 00 CO t*« C^b»COOO'Tl O CO C<
•5 jSSoSS SSS§g oooo^ 8SS8S SSSSS $2S2^
s i ° P o" ' ' " " O* " " " ' O* " * * * O*
.
^CMOl>*O
COI>OOOOOS
16
CHAPTER 1. AIR, WATER AND STEAM
Q
W
D
2
O
u
3
o^oow weocqiH tHw^sco "iooooo icr-o^o r-o«ooo»-i owiH»-ieq
OS "<Ji 00 Ofl t* »-ieOiHCOiH ?0iHtOi-U> <N 00 COOS"? »-i t» ^) O t* cCOt*-rt<Cl Osf»»OCO*-i
cqcOOQ^Tl* lOUiCOtOtS b«OOOOOSOJ OOHi-iN CCCOriiUtSiO eSt^t^OOQ OOiHCQM
rt^iHiHrH ^rtrHrtrt M rl rH rt rl <N <M N (N N <N N « d W <NN<NN<N NCOCOCOCC
CO CO 00 f^ CO USOOOWO
oooocooici csaso'o'd
QOON-i-iiO OCOt^iHUi CSC
S<N^b-GS iiTjisOOiiH Wt
o
>O
Sl^OCOO OsWOOOiH tKI>OCOCO OS<NtOO(N IOO5
>COCO(O Ot^t^t^OO OOOOC5OO5 OOOO«-i i-trHC
WNNNN NNWNN WNNDJCQ dCCMCOCC COCOMCOCO CCCOWCOW eOWCCCOCO
pHrHi-^THf-H ^H iH TH T-l r-l rHrlfHiHrH iH rl rH r-l i-H i-l r-(»H iH i-H iH i-l i-( iH T-t 1-(T-HHtHi-H
s
a
i
Q
w
H
P-.
CD
5i-l WONOSrH T}icCOJT-c* t"-OWOOS (NU3CSNO
mo io»ftioioo ooot^t^ t-ooooooco osoooo
I
i«o T^t-noc
Boo ooooo ooooo
eoeoeoeoco
Ot- CSN^h
o"3O£iO
SOOOi-i
8888
I
!I
w
•s
c
OIOC
NC^lNlNfN
Hi-4CO^Ot« iHiOi-^OCO OOBOOQOO C\)U5
O CO CO CO CO CO CO CO ^ ^ •^•^•^•^lO lOiQU
s
^
IACOt*OOQ Oi-i(NOOTjH tOOb-000) e«H
woocoeoco ^^««t<-^^ ^<^^^^ ujio
HEATING VENTILATING Am CONDITIONING GUIDE 1938
g g j I>SIO»MIS c^sswoo CTr*i-«eo »oo~*«ooco r^NOrsio o-^csccoo
'' ''
I ;SII11 SSSSS SSSSS SS'SS
\ ** 'S ; COOCO COCOO OOOOO OOOOO O*Hi-HtHr-l fHiHiHiHi-4 ,-HHiHTH
5 '
js i
=1 u=:
'. £«
""t*
~<I
*&
rf i "J
H i
i!
< ; s
> £
^•^(Nt-^C
U3 Q5b»OOC
WIN (N CMP
I « ' '
I
'
c I
SSfeSS b^^6;* ooSw^^ 5§S
^g^^g £§£££ Sgggg^ «S
S8888 88888 88888 888ii lilil Illli §§§§§
® ° o o X " * " " M •••••••..
SS
o«e»^« «W!»s isssfe gggss g
TJJ3J52GSN 5*t«
00 00 OOOOO) OO
18
CHAPTER 1. Am, WATER AND STEAM
I
fij
3 a
2QCOO«* «O»HOGCD OCOWOO OSrHNMeO CO'Ht'-.O
OiHOQio ooc*t<-o4r» TjHrHosoooo QOOMOO xaoioooo
fflOI>b-oO OooOS
OOOOO OOO
rtua OTJHOSOOOO wt
OO ^*tHtHoJoiJ COC
rt^iHi-lrH iH i
N«cOi-no
NOOOOOSoi
i-t T-l rH iH 1-1
*i
£s
58
i
^^Or*'* iHOOWCOO OOCOrticq»-« OOOQONr>- OOt*.t^OO OiHCOiOh. O0
03^10*0(0 t-t-WOJO O^NCO-* 10 10 Ot* 00 0» Oi-4C4 CO TPOI>OOC> rH
iflifstouso ?c5o«o«oo (O«o«odt3 <ONNt^»^ Nlt^t^t^i^ 0606000606
OW iOh-O5CM»O t-pCM«3t*. OWiCl^O NO
CO CO COCOCOTJI^ ^QiO>0>Q OOOOt* t^b-
lOr-iQ ^MND
eOrfrH
o
•5
OCCDDCO COWSOC
cotoocQcr
OOiHlOfHC
b.t>COCOCC
oo«5^c<
ptcouibo
rH*OOS"5CO i-tr-tCi
3*»SP« wgor
•3
a
oeoeoweo co coco coco
s
gt
a
s
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
a
5
g
N
Z
&
<
&&*
c
H
fc*
O
pf
<
?
&
>
^
1
tf
D
H
fa
O
£§!"' JSS5
£33S SS38S 3SS8S SSSSS 35323 35353
S.*6* 2 ' *a pi *» *<9 •* **•*»(* is* «s OI^N-OOOO essscsoo
jsSJja I ?J?<5'5MS MNWN?? tjNNww WNNCOM
§ ;*-»*••: ss re i- ^
-2 c.*^s?u's ^. .
!^ ! rcw»f •»*-* ^jJujttiiius occcotoo i^h^t^boo
H CCSCWMC? -cwwccw rtccwccec coMcoroeo
csoi-<»- iHi-
(N «N <N (N N OTN
I "* j?
ie 15 us in is
>OQOOMU3 OOPMOOO i-tCO5OQO»H COeOOOr-ieO COOO«HCO«O
WMn4T}J^4 ^jSSiOioSS tfSCOOOb- N-fr-lNOOOO OOOOO»»O
i^'iftL'iiflio iQto'ioia'to loioiousio 10 us* us us* us toioioioio
rHr-liHi-li-l ,H rH »H iH i-l iH »-4 »H ^1 i-t ^^Hrt^HH rH i-l iH iH T-(
I
K
g
j2
s
ooo»osoo«o
OCOiH^Ici
OlOiHN-* lOOOOOir-l N-t
NCCCOWS MMOOM^ ^r
o* o* o"
iHOS»-tN.eO
CO*-iCOOiO
oooooseo soi-io»-(t
S ooooo ooooo Soooo ooooo ooooo
Ilill
coeo'cocooo
looooo oo'h'f.V* N.Vb."oo"oo ooooooos'os" ojoooo o^*4rtj4 nnneoeQ
sssss
20
CHAPTER 1. AIR, WATER AND STEAM
Q
W
Q
I
5
i
g
£
8
ta
o
I
rt
I
Q
g
I
co
w
n
5s
S
I
&
QiHOiH ij* OJ t* 00 »•*
OONS OOiHiftO-^
Ocpr— r» r- 00 00 00 O
O<^a»COOO 04
00 1-1 COO 00 I-H CO CO 00 i-l OQCOOQv-l-44 CD O5 »-!•<# CO Or-C^COO *-<
C3JOOOO iHiHiHiHM (N CNN CO CO COCO^-*-* r!J>O»O»O«O «o
lAcdcococo co cd co* «o co* ed co co co CD co' co* co' co co* co'co'co'coco co*
«OCOOJWU5 b-iOb-b-OO eOiH-^i-105 OOOOO OOOOO O
O O" O " " "rH r^T^rHiHiH
iQoooe
t-i^H^fHtH T-KNCQCvKN
CDOOOO OOOOO
SiH CO Is- I-H t>.
0001-1^ »-*
I
10 10 to «0 to ivi>»oooo asasos
- - - - - --
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Via (Wv - W) = c^ (t - *') + c»sW (t - *') (9a)
and using cPa « 0.24 and c^ = 0.45
fcff8 (Wti - WO - (0.24 + 0.45J7) (/ - *•) (9b)
where
A!fg « latent heat of vaporization at t\ Btu per pound.
(Wt*f— W} = increase in vapor associated with 1 Ib of dry air when it is saturated
adiabatically from an initial dry-bulb temperature, tt and an initial vapor content, W.
pounds.
Knowing any two of the three primary variables, t, t', or W, the third
may be found from this equation for any process of adiabatic saturation.
TOTAL HEAT AND HEAT CONTENT
The total heat of a mixture of dry air and water vapor was originally
defined by W. H. Carrier as
S - c^(t - 0) + W [A'fg + c^(t - /')] (10)
where
S = total heat of the mixture, Btu per pound of dry air.
£pa ™ raean specific heat at constant pressure of dry air.
Cpg — mean specific heat at constant pressure of water vapor.
/ = dry-bulb temperature, degrees Fahrenheit.
t1 = wet-bulb temperature, degrees Fahrenheit.
W = weight of water vapor mixed with each pound of dry air, pounds.
#fg = latent heat of vaporization at t1, Btu per pound.
Since this definition holds for any mixture of dry air and water vapor,
the total heat of a mixture with a relative humidity of 100 per cent and at
a temperature equal to the wet-bulb temperature (/') is
By equating Equation lOto Equation 11, the equation for the adiabatic
saturation process, Equation 9a, follows. This demonstrates that the
adiabatic saturation process at constant wet-bulb temperature is also a
process of constant total heat. In short, the total heat of a mixture of dry
air and water vapor is the same for any two states of the mixture at the
same wet-bulb temperature. This fact furnishes a convenient means of
finding the total heat of an air-vapor mixture in any state.
Enthalpr
T, J?iS to.tal.heat of J^ air-vapor mixture is not exactly equal to the true
heat content;or enthalpy of the mixture since the heat content of the
liquid is not included in Equation 10. With the meaning of hea? content
m agreement with present practise in other branches of liermodynamics
the true heat content of a mixture of dry air and water vapor (SthTp
?oSr ?he S&ol^ and the "^^ *** at 32 F « tie datum
22
CHAPTER 1, AIR, WATER AND STEAM
h « cPa (t - 0) -f W h9 = 0.24 (* - 0) + W ks (12)
where
h — the heat content of the mixture, Btu per pound of dry air.
t = the dry-bulb temperature, degrees Fahrenheit.
W = the weight of vapor per pound of dry air, pounds.
hs = the heat content of the vapor in the mixture, Btu per pound.
The heat content of the water vapor in the mixture may be found in
steam charts or tables when the dry-bulb temperature and the partial
pressure of the vapor are known. Or, since the heat content of steam at
low partial pressures, whether super-heated or saturated, depends only
upon temperature, the following empirical equation, derived from Proper-
ties of Saturated Steam by J. H. Keenan, Table 8, may be used:
hs - 1059.2 + 0.45 /' (13)
Substituting this value of h& in Equation 12, the heat content of the
mixture is
h = 0.24 (t - 0) + W (1059.2 + 0.45 *!) (14)
Example 5. Find the total heat of an air-vapor mixture having a dry-bulb tem-
perature of 85 F and a wet-bulb temperature of 70 F.
Solution. From Table 6, for saturation at the wet-bulb temperature, W£ = 0.01574,
and from Equation 14,
h = 0.24 (70-0) + 0.01574 [1059.2 + (0.45 X 70)] = 33.96 Btu per pound dry air.
By considering the temperatures in Table 6 to be wet-bulb readings, the
enthalpy of any air-vapor mixture may be obtained from the last column
in the table.
An energy equation can be written that applies, in general, to various
air conditioning processes, and this equation can be used to determine the
quantity of heat transferred during such processes. In the most general
form, this equation may be explained with the aid of Fig. 1 as follows.
The rectangle may represent any apparatus, e.g., a drier, humidifier, dehumidifier,
cooling tower, or the like, by proper choice of the direction of the arrows.
In general, a mixture of air and water vapor, such as atmospheric air, enters the
apparatus at 1 and leaves at 3. Water is supplied at some temperature, &. For the flow
of 1 Ib of dry air (with accompanying vapor) through the apparatus, provided there is no
appreciable change in the elevation or velocity of the fluids and no mechanical energy
delivered to or by the apparatus,
h + £h + (W, - W,) A, = h, + Re
or
Eh - RC - h, - A, - (W, - W,) A,' (15)
where
Eh = the quantity of heat supplied per pound of dry air, Btu.
RC — the quantity of heat lost externally by heat transfer from the apparatus.
Btu per pound of dry air.
Wi = the weight of water vapor entering, per pound of dry air.
Wz — the weight of water vapor leaving, per pound of dry air.
}i* =» the heat content of the water supplied at h, Btu per pound.
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Aa — hi = the increase in the heat content of the air-water vapor mixture in passing
through the apparatus, Btu per pound of dry air
- 0.24 (/, - ft) + Wi (1059.2 + 0.45 /») - Wi (1059.2 + 0.45fc)
The net quantity of heat added to or removed from air-water vapor
mixtures in air conditioning work is frequently approximated by taking
the differences in total heat at exit and entrance.
For example, in Fig. 1, an approximate result is
£h - -Re = Sa - Si (16)
where
Sj « the total heat of the air- vapor mixture at exit, Btu per pound of dry air.
Si •• the total heat of the air-vapor mixture at entrance, Btu per pound of dry air.
Wi Ib, Water Vapor
lib. Dry Air
W3 Ib. Water Vapor
lib. Dry Air
r?r
<W5-H$)lb. Water
FIG. 1. DIAGRAM ILLUSTRATING ENERGY EQUATION 15
From the definitions of total heat and heat content, it may be demon-
strated that Equation 16 is exactly equivalent to Equation 15, when, and
only when, t\ = t\ = fa; i.e., when the initial and final wet-bulb tempera-
tures and the temperature of the water supplied are equal. The one pro-
cess that meets these conditions is adiabatic saturation, and either
equation will give a^result of zero; for other conditions, Equation 16 is
approximate but satisfactory for many calculations.
The following problems illustrate the application of these principles:
&cample 6. Heating (data from Example 2). Assuming the water to be supplied at
60 F, the net quantity of heat supplied is, from Equation 15,
£h - Re - 0.24 (70 - 0) + 0.000548 X 0.45 (70 - 0) + 0.005632
[1059.2 + 0.45 X 70 - (50 - 32)] - 22.90 Btu per pound of dry air.
Cooling (data from Example 3). If the condensate is removed at 54 F
— * removed is found from Equation 15, by proper regard to the arrow
£fa + #c - 0.24 (84 - 54) + 0.00887 X 0.45 (84 - 54) + 0 00361
[1059.2 + 0.45 X 84 - (54 - 32)] - 11. 24 Btu per pound of dry air.
«*«-> — the wet-bulb
fr°-m ^K6' since ** «£t air is saturated, 22.55 Btu per
quantity of heat removed is, approximately
f dry air< The degree °f appr-mat- ^
24
CHAPTER 1. AIR, WATER AND STEAM
PSYCHROMETRIC CHART
The revised Bulkeley Psychrometric Chart4, will be found attached to
the inside back cover. It shows graphically the relationships expressed
in Equations 9a and 9b. It also gives the grains of moisture per pound of
dry air for saturation, the grains of moisture per cubic foot of saturated
air, the total heat in Btu per pound of dry air saturated with moisture,
and the weight of the dry air in pounds per cubic foot. Fig. 2 shows the
procedure to follow in using the Bulkeley Chart. The directrix curves
above the saturation line are as follows:
A is the total heat in Btu contained in the mixture above 0 F, and is to be referred
to the column of figures at the left side of the chart. Heat of the liquid is not included.
A, B, C, D, E, FaDirectrix lines
D. B. L»Dry bulb line
D. P. L=Dew point line
R. H. L=Relative humidity line
W.B.1_= Wet bulb line
Sl= Saturation line
G. P. Lb» Grains moisture sat mixture per Ib dry air R. D. D. S.= Relative density dry air per cu ft saturated
T. H.=Total heat sat mixture per Ib dry air W. P. C. F. S.= Weight per cu ft in Ibs saturated
V. P.»Vapor pressure in mm mercury R. D. S.*Relative density per cu ft saturated
G. P. C. F. S.=Grains moisture per cu ft sat air W. P. C. F. D.» Weight per cu ft in Ibs dry
W. D. A. C. F. S.=Weight dry air per cu ft in Ibs saturated R. D. D.=Relative density per cu ft dry
W. P. C. F. x
R. D.x
- w- p- c- F- * parta' MturaBon
FIG. 2 DIAGRAMS SHOWING PROCEDURE TO FOLLOW IN USING BULKELEY CHART
B is the grains of moisture of water vapor contained in each pound of the saturated
mixture and is to be referred to the figures at the left side of the chart.
C is the grains of moisture of water vapor per cubic foot of saturated mixture, and is
to be referred to the figures at the left side of the chart which are to be divided by 10.
D is the weight in decimal fractions of a pound of dry air in one cubic foot of the
saturated mixture, and is referred to the first column of figures to the right of the satura-
tion line between the vertical dry-bulb temperature lines 170 and 180 F. The relative
density of the mixture is read in a similar manner from the same curve by the column of
figures between the vertical dry-bulb temperature lines 180 and 190 F.
E is similar to D but is for one cubic foot of the saturated mixture.
«The Bulkeley Psychrometric Chart was presented to the Society in 1926. (See A.S.H.V.E. TRANS-
ACTIONS, Vol. 32, 1926, p. 163.) Single copy of the chart can be furnished at a cost of $ .25.
HEATING VENTIUITING AIR CONDITIONING GUIDE 1938
F is similar to D but is for dry air, devoid of all moisture or water vapor. For con-
venience, the approximate absolute temperature of 500 F is given at 40 F on the satura-
tion line for the purpose of calculating volume, weight per cubic foot, and relative density
at partial saturation.
METHOD OF USING THE CHART
Relati
__., line, t
as 46 per cent.
Example 8. Relative Humidity: At the intersection of the 78 F wet-bulb line and the
95 F dry-bulb line, the relative humidity is read directly on the straight diagonal lines
as 46 per cent.
Example 9. Dew Point: At the intersection of the 78 F wet-bulb line, the dew-point
temperature is read directly on the horizontal temperature lines as 70.9 F.
Example 10. Vapor Pressure: At the intersection of the 78 F wet-bulb line and the
95 F ^dry-bulb line, pass in a horizontal direction to the left of the chart and on the
logarithmic scale read the vapor pressure as 19.4 millimeters of mercury. (Divide by
25.4 for inches.)
Example 11. Total Heat Above 0 F in Mixture per Pound of Dry Air Saturated with
Moisture: From where the wet-bulb line joins the saturation line, pass in a vertical
direction on the 78 F dry-bulb line to its intersection with curve A and on the logarithmic
scale aMhe left of the chart read 40.6 Btu per pound of mixture. The use of this curve
to obtain the total heat in the mixture at any wet-bulb temperature is a great con-
venience, as the number of Btu required to heat the mixture and humidify it, as well as
the refrigeration required to cool and dehumidify the mixture, can be obtained by
taking the difference in total heat before and after treatment of the mixture.
Example 12. Grains of Moisture per Pound of Dry Air Saturated with Moisture:
From 70.9 F dew-point temperature on the saturation line, pass vertically to the inter-
section with curve B and on the logarithmic scale at the left read 114 grains of moisture
per pound.
Example 1$.^ Grains of Moisture per Cubic Foot of Mixture, Partially Saturated: From
/0.9 F dew-point temperature on the saturation line proceed in a vertical direction to
curve C, and on the logarithmic scale to the left read 83.3 which, divided by 10 gives
S.d3 grains. A temperature of 70.9 F is equal to an absolute temperature of 530.9, and
95 F equals 555, absolute temperature. Therefore, ^ x 8>33 . 7 97 gr^n& pcf
cubic foot of partially saturated mixture.
Example 14. Grains of Moisture per Cubic Foot of Saturated Air: Starting at the
saturation line at the desired temperature, pass in a vertical direction to curve C and on
the logarithmic scale at the left, read a number which, divided by 10, will give the
answer.
Example IS. Weight per Cubic Foot of Dry A ir and Relative Density: From the point
±^rr3mTKe'vhe 1? F< vertical dry'bulb Iine intersects curo £- Pass to rightP° We
and read 0.075 Ib; if cubic feet per pound are desired, divide 1 by this amount The
relative density is read immediately to the right as 1.00. <"«UUni. me
i" per C^Foot °f Saturated Mixture and Relative
Vn t r,v '-f°r exafflP'e, the 70 F vertical line intersects the curve
£ £4,7"* per cublc foot as °-07316
Partially
si
Therefore, ^ = 0.851. The weight of 1 cu ft of air at 50 F dry-bulb and 46 F wet-bulb
x °'851 = a°6675- and the relative dens*v » 1-046
26
CHAPTER 1. AIR, WATER AND STEAM
PROPERTIES OF WATER
Composition of Water. Water is a chemical compound (H2O) formed by
the union of two volumes of hydrogen and one volume of oxygen, or two
parts by weight of hydrogen and 16 parts by weight of oxygen.
Density of Water. Water has its greatest density at '39.2 F, and it
expands when heated or cooled from this temperature. At 62 F a U. S.
gallon of 231 cu in. of water weighs approximately 8% Ib, and a cubic foot
of water is equal to 7.48 gal. The specific volume of water depends on the
temperature and it is always the reciprocal of its density. (See Table 7.)
TABLE 7. THERMAL PROPERTIES OF WATER
TEMPERATURE
DEGF
SAT. PRESS.
LB PER SQ IN.
VOLUME Cu FT
raaLs
WEIGHT LB PER
CuFi
SPECIFIC
HEAT
32
0.0887
0.01602
62.42
1.0093
40
0.1217
0.01602
62.42
1.0048
50
0.1780
0.01602
62.42
1.0015
60
0.2561
0.01603
62.38
0.9995
70
0.3628
0.01605
62.31
0.9982
80
0.5067
0.01607
62.23
0.9975
90
0.6980
0.01610
62.11
0.9971
100
0.9487
0.01613
62.00
0.9970
110
1.274
0.01616
61.88
0.9971
120
1.692
0.01620
61.73
0.9974
130
2.221
0.01625
61.54
0.9978
140
2.887
0.01629
61.39
0.9984
150
3.716
0.01634
61.20
0.9990
160
4.739
0.01639
61.01
0.9998
170
5.990
0.01645
60.79
1.0007
180
7.510
0.01650
60.61
1.0017
190
9.336
0.01656
60.39
1.0028
200
11.525
0.01663
60.13
1.0039
210
14.123
0.01669
59.92
1.0052
212
14.696
0.01670
59.88
1.0055
220
17.188
0.01676
59.66
1.0068
240
24.97
0.01690
59.17
1.0104
260
35.43
0.01706
58.62
1.0148
280
49.20
0.01723
58.04
1.0200
300
67.01
0.01742
57.41
1.0260
350
134.62
0.01797
55.65
1.0440
400
247.25
0.01865
53.62
1.0670
450
422.61
. 0.01950
51.30
1.0950
500
681.09
0.02050
48.80
1.1300
550
1045.4
0.02190
45.70
1.2000
600
1544.6
0.02410
41.50
1.3620
700
3096.4
0.03940
25.40
Water Pressures. Pressures are often stated in feet or inches of water
column. At 62 F, with h equal to the head in feet, the pressure of a
column of water is 62.383fe Ib per square foot, or 0.433fe Ib per square inch.
A column of water 2.309 ft (27.71 in.) -high exerts a pressure of one pound
per square inch at 62 F.
Boiling Point of Water. The boiling point of water varies with the
pressure; it is lower at higher altitudes. A change in pressure will always
be accompanied by a change in the boiling point, and there will be a cor-
27
HEATING
VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 8. PROPERTIES OF
Specific Volume
££/*!?&. SS'F. l££id Erap. V?^r
p t Vf Vfc vg
WH* 58.83 0.01603 1256.9 1256.9
SATURATED STEAM:
Total Heat
Sat. Sat.
Liquid Evap. Vapor
hf hfg tr«
26.88- 1058.8 1085.7
PRESSURE TABLE*
Entropy
Liquid Evap. Vapor Lb./Sq. JS£
8f * Sfg Sg p
0.0533 2.0422 2.0955 WH*
%"H& 70.44
0.01605
856.5
856.5
38.47
10523
1091.0
0.0754
1.9856 2.0609
%"Hff
l"Hj
r 79.06
0.01607
652.7
652.7
47.06
1047.8
1094.9
0.0914
1.9451
2.0365
l"Hff
V&" Hi
r 91.75
0.01610
4453
4453
59.72
1040.8
1100.6
0.1147
1.8877
2.0024
WHff
2"H* 101.17
0.01613
339.5
3393
69.10
1035.7
1104.8
0.1316
1.8468
1.9784
2" Hi
2'4"Hfi
r 108.73
0.01616
2752
2752
76.63
10313
1108.1
0.1450
1.8148
1.9598
2i/2;;Hff
3"Hgr 115.08
0.01618
231.8
231.8
82.96
1027.9
1110.8
0.1561
1.7885
1.9446
1.0
101.76
0.01614
333.8
333.9
69.69
10353
1105.0
0.1326
1.8442 1.9769
1.0
2.0
126,10
0.01623
173.94
173.96
93.97
1021.6
1115.6
0.1750
1.7442
1.9192
2.0
3.0
141.49
0.01630
118.84
118.86
10933
1012.7
1122.0
02009
1.6847
1.8856
3.0
4.0
152.99
0.01636
90.72
90.74
120.83
1005.9
1126.8
02198
1.6420
1.8618
4.0
5.0
16225
0.01641
7339
73.61
130.10
1000.4
1130.6
02348
1.6088
1.8435
5.0
6.0
170.07
0.01645
62.03
62.05
137.92
995.8
1133.7
02473
13814
1.8287
6.0
7.0
176.85
0.01649
53.68
53.70
144.71
991.7
1136.4
0.2580
13582
1.8162
7.0
8.0
182.87
0.01652
4738
4739
150.75
988.1
1138.9
02674
1.5379
1.8053
8.0
9.0
18828
0.01*656
42.42
42.44
156.19
984.8
1141.0
02758
13200
1.7958
9.0
10.0
19321
0.01658
38.44
3-8.45
161.13
981.8
1143.0
0.2834
13040
1.7874
10.0
11.0
197.75
0.01661
35.15
35.17
165.68
979.1
1144.8
02903
1.4894
1.7797
11.0
12.0
201.96
0.01664
32.40
3Z.42
169.91
9763
1146.4
02968
1.4760
1.7727
12.0
13.0
205.88
0.01666
30.06
30.08
173.85
974.1
1147.9
03027
1.4636
1.7663
13.0
14.0
209.56
0.01669
28.05
28.06
177.55
971.8
11493
03082
1.4521
1.7604
14.0
14,696
212.00
0.01670
26.80
26.82
180.00
9702
1150.2
03119
1.4446
1.7564
14.696
16.0
21632
0.01673
24.75
24.76
18435
967.4
1151.8
03184
1.4312
1.7496
16.0
18.0
222.40
0.01678
22.16
22.18
190.48
9633
1154.0
03274
1.4127
1.7402
18.0
20.0
227.96
0.01682
20.078
20.095
196.09
959.9
1156.0
03356
13960
1.7317
20.0
22.0
233.07
0.01685
18363
18380
20125
956.6
1157.8
03431
13809
1.7240
22.0
24.0
237.82
0.01689
16.924
16.941
206.05
953.4
11593
03500
13670
1.7170
24.0
26.0
242.25
0.01692
15.701
15.718
210.54
950.4
1161.0
03564
13542
1.7106
26.0
28.0
246.41
0.01695
14.647
14.664
214.75
947.7
1162.4
03624
13422
1.7046
28.0
30.0
25034
0.01698
13.728
13.745
218.73
945.0
1163.7
03680
13310
1.6990
30.0
32.0
254.05
0.01701
12.923
12.940
222.50
942.5
1165.0
03732
13206
1.6938
32.0
34.0
36.0
38.0
257.58
260.94
264.16
0.01704
0.01707
0.01710
12209
11.570
10.998
12226
11.587
11.015
226.09
22931
232.79
940.0
937.7
9353
1166.1
11672
11683
03783
03830
03876
13107
13014
12925
1.6890
1.6844
1.6800
34.0
36.0
38.0
40.0
42.0
44.0
46.0
48.0
26724
27021
273.06
275.81
278.45
0.01712
0.01715
0.01717
0.01719
0.01722
10.480
10.010
9.582
9.189
8.829
10.497
10.027
9399
9207
8.846
235.93
238.95
241.86
244.67
24737
9333
9312
9292
9272
925.4
11692
11702
1171.1
1171.9
1172.7
03919
03961
0.4000
0.4039
0.4076
12840
12759
12682
12608
12537
1.6759
1.6720
1.6683
1.6647
1.6613
40.0
42.0
44.0
46.0
48.0
60.0
52.0
54.0
66.0
68.0
281.01
283.49
285.90
28823
290.50
0.01724
0.01726
0.01728
0.01730
0.01732
8.496
8.189
7.902
7.636
7388
8.514
8206
7.919
7.653
7.405
249.98
25232
254.99
25738
259.71
923.5
921.7
920.0
9183
916.6
11733
11743
1175.0
1175.7
1176.4
0.4111
0.4145
0.4178
0.4210
0.4241
12469
12404
1.2340
12279
12220
1.6580
1.6549
1.6518
1.6489
1.6461
50.0
62.0
54.0
56.0
58.0
60.0
62.0
64.0
66.0
68.0
292.71
294.85
296.94
298.98
300.98
0.01735
0.01737
0.01739
0.01741
0.01743
7.155
6.937
6.732
6.539
6357
7.172
6.955
6.749
6356
6375
261.98
264.18
26633
268.43
270.49
915.0
913.4
911.9
910.4
908.9
1177.0
1177.6
11782
1178.8
1179.4
0.4271
0.4300
0.4329
0.4356
0.4384
12162
12107
12053
12001
1.1950
1.6434
1.6407
1.6382
1.6357
1.6333
60.0
62.0
64.0
66.0
68.0
70.0
72.0
74.0
76.0
78.0
302.92
304.82
306.68
30830
31028
0.01744
0.01746
0.01748
0.01750
0.01752
6.186
6.024
5.870
5.723
5384
6203
6.041
5.887
5.741
5.602
272.49
274.45
27637
27825
280.09
907.4
906.0
904.6
9032
901.9
1179.9
1180.5
1181.0
11813
1182.0
0.4410
0.4435
0.4460
0.4485
0.4509
1.1900
1.1852
1.1805
1.1759
1.1714
1.6310
1.6287
1.6265
1.6244
1.6223
70.0
72.0
74.0
76.0
78.0
80.0
82.0
84.0
86.0
88.0
312.03
313.74
315.42
317.06
318.68
0.01754
0.01756
0.01757
0.01759
0.01761
5.452
5325
5204
5.089
4.979
5.470
5343
5222
5.107
4.997
281.90
283.67
285.42
287.13
288.80
900.5
8992
897.9
896.7
895.4
1182.4
1182.9
1183.4
1183.8
11842
0.4532
0.4555
0.4578
0.4599
0.4621
1.1670
1.1627
1.1586
1.1545
1.1505
1.6202
1.6182
1.6163
1.6144
1.6126
80.0
82.0
84.0
86.0
88.0
90.0
92.0
94.0
96.0
98.0
32027
321.83
32337
324.88
32637
0.01763
0.01764
0.01766
0.01768
0.01769
4.874
4.773
4.676
4384
4.494
4.892
4.791
4.694
4.602
4.512
290.45
292.07
293.67
29525
1296.80
8942
893.0
891.8
890.6
889.4
1184.6
1185.0
1185.4
1185.8
1186.2
0.4642
0.4663
0.4683
0.4703
0.4723
1.1465
1.1427
1.1389
1.1352
1.1316
1.6107
1.6090
1.6072
1.6055
1.6038
90.0
92.0
94.0
96.0
98.0
28
CHAPTER 1. AIR, WATER AND STEAM
TABLES. PROPERTIES OF SATURATED STEAM: PRESSURE TABLE — (Continued)
Specific Volume
Total Heat
Entropy
Ab*. Pr*»«.
Lb./Sq. In.
BSfe
Sat. Sat.
Liquid Evap. Vapor
Sat. Sat.
Liquid Evap. Vapor
Liquid Evap. Vapor
Ab*. Pr*M.
Lb./Sq. In.
P
t
Vf Vfg Vg
hf hfg hK
Sf Sfg Sff
P
100.0
327.83
0.01771 4.408 4.426
29833 888.2 1186.6
0.4742 1.1280 1.6022
100.0
102.0
329.27
0.01773 4326 4344
299.83 887.1 1186.9
0.4761 1.1245 1.6006
102.0
104.0
330.68
0.01774 4.247 4.265
30130 886.0 11873
0.4779 1.1211 1.5990
104.0
106.0
332.08
0.01776 4.171 4.189
302.76 884.9 1187.6
0.4798 1.1177 1.5974
106.0
108.0
333.44
0.01777 4.097 4.115
304.19 883.8 1188.0
0.4816 1.1144 1.5959
108.0
110.0
334.79
0.01779 4.026 4.044
305.61 882.7 11883
0.4834 1.1111 1.5944
110.0
112.0
336.12
0.01780 3.958 3.976
307.00 881.6 1188.6
0.4851 1.1079 1.5930
112.0
114.0
337.43
0.01782 3.892 3.910
30836 880.6 1188.9
0.4868 1.1048 1.5915
114.0
116.0
338.72
0.01783 3.828 3.846
309.71 879.5 1189.2
0.4885 1.1017 1.5901
116.0
118.0
340.01
0.01785 3.766 3.784
311.05 878.5 1189.5
0.4901 1.0986 1.5887
118.0
120.0
341.26
0.01786 3.707 3.725
31237 877.4 1189.8
0.4918 1.0956 1.5874
120.0
122.0
342.50
0.01788 3.652 3.670
313.67 876.4 1190.1
0.4934 1.0926 1.586Q
122.0
124.0
343.73
0.01789 3.597 3.615
314.96 875.4 1190.4
0.4950 1.0897 1.5847
124.0
126.0
344.94
0.01791 3.542 3.560
316.23 874.4 1190.6
0.4965 1.0868 1.5834
126.0
128.0
346.14
0.01792 3.487 3.505
317.49 873.4 1190.9
0.4981 1.0840 1.5821
128.0
130.0
347.31
0.01794 3.433 3.451
318.73 872.4 1191.2
0.4996 1.0812 1.5808
130.0
132.0
348.48
0.01795 3383 3.401
319.95 871.5 1191.4
0.5011 1.0784 1.5796
132.0
134.0
349.64
0.01796 3335 3353
321.17 870.5 1191.7
0.5026 1.0757 1.5783
134.0
136.0
350.78
0.01798 3.288 3306
32237 869.6 1191.9
0.5041 1.0730 1.5771
136.0
138.0
351.91
0.01799 3.242 3.260
323.56 868.6 1192.2
0.5056 1,0703 1.5759
138.0
140.0
353.03
0.01801 3.198 3.216
324.74 867.7 1192.4
0.5070 1.0677 1.5747
140.0
142.0
354.14
0.01802 3.155 3.173
325.91 .866.7 1192.6
0.5084 1.0651 1.5735
142.0
144.0
355.22
O.Q1804 3.112 3.130
327.06 865.8 1192.9
0.5098 1.0625 1.5724
144.0
146.0
35631
0.01805 3.071 3.089
328.20 864.9 1193.1
0.5112 1.0600 1.5712
146.0
148.0
35737
0.01806 3.031 3.049
32932 864.0 11933
0.5126 1.0575 1.5701
148.0
150.0
358.43
0.01808 2.992 3.0'10
330.44 863.1 1193.5
0.5140 1.0550 1.5690
150.0
152.0
359.47
0.01809 2.954 2.972
331.54 862.2 1193.7
0.5153 1.0526 1.5679
152.0
154.0
360.51
0.01810 2.917 2.935
332.64 8613 1193.9
0.5166 1.0502 1.5668
154.0
156.0
361.53
0.01812 2.882 2.9QO
333.72 860.4 1194.1
0.5180 1.0478 1.5658
156.0
158.0
362.54
0.01813 2.846 2.864
334.80 859.5 11943
0.5193 1.0454 1.5647
158.0
160.0
363.55
0.01814 2.812 2.830
335.86 858.7 1194.5
0.5205 1.0431 1.5636
160.0
162.0
364.54
0.01816 2.779 2.797
336.91 857.8 1194.7
0.5218 1.0408 1.5626
162.0
164.0
365.52
0.01817 2.746 2.764
337.95 857.0 1194.9
0.5230 1.0385 1.5616
164.0
166.0
366.50
0.01818 2.715 2.733
338.99 856.1 1195.1
0.5243 1.0363 1.5606
166.0
168.0
367.46
0.01819 2.683 2.701
340.01 855.2 11953
0.5255 1.0340 1.5596
168.0
170.0
368.42
0.01821 2.653 2.671
341.03 854.4 1195.4
0.5268 1.0318 1.5586
170.0
172.0
369.37
0.01822 2.623 2.641
342.04 853.6 1195.6
0.5280 1.0296 1.5576
172.0
174.0
370.31
0.01823 2.594 2.612
343.04 852.7 1195.8
0.5292 1.0275 1.5566
174.0
176.0
371.24
0.01825 2.566 2.584
344.03 851.9 1196.0
0.5304 1.0253 1.5557
176.0
178.0
372.16
0.01826 2.538 2.556
345.01 851.1 1196.1
0.5315 1.0232 1.5548
178.0
180.0
373.08
0.01827 2.511 2.529
345.99 8503 1196.3
0.5327 1.0211 1.5538
180.0
182.0
374.00
0.01828 2.484 2.502
346.97 849.5 1196.4
0.5339 1.0190 1.5529
182.0
184.0
374.90
0.01829 2.458 2.476
347.94 848.6 1196.6
0.5350- 1.0169 1.5520
184.0
186.0
375.78
0.01831 2.433 2.451
348.89 847.9 1196.8
0.5362 1.0149 1.5511
186.0
188.0
376.67
0.01832 2.407 2.425
349.83 847.1 1196.9
0.5373 1.0129 1.5502
188.0
190.0
377.55
0.01833 2383 2.401
350.77 8463 1197.0
0.5384 1.0109 1.5493
190.0
192.0
378.42
0.01834 2359 2377
351.70 845.5 1197.2
0.5395 1.0089 1.5484
192.0
194.0
379.27
0.01835 2335 2353
352.61 844.7 11973
0.5406 1.0070 1.5475
194.0
196.0
380.13
0.01837 2312 2330
353.53 844.0 1197.5
0.5417 1.0050 1.5467
196.0
198.0
380.97
0:01838 2.289 2307
354.43 843.2 1197.6
0.5427 1.0031 1.5458
198.0
200.0
381.82
0.01839 2.267 2.285
35533 842.4 1197.8
0,5438 1.0012 1.5450
200.0
205.0
383.89
0.01842 2.213 2.231
357.56 840.5 1198.1
0.5465 0.9964 1.5429
205.0
210.0
385.93
0.01844 2.162 2.180
359.76 838.6 1198.4
0.5491 0.9918 1.5409
210.0
215.0
387.93
0.01847 2.113 2.131
361.91 836.8 1198.7
0.5516 0.9873 1.5389
215.0
220.0
389.89
0.01850 2.066 2.084
364.02 835.0 1199.0
0.5540 0.9829 1.5369
220.0
225.0
391.81
0.01853 2.0208 2.0393
366.10 833.2 11993
0.5565 0.9786 1.5350
225.0
230.0
393.70
0.01856 1.9778 1.9964
368.14 831.4 1199.6
0.5588 0.9743 1.5332
230.0
235.0
395.56
0.01859 1.9367 1.9553
370.15 829.7 1199.8
0.5612 0.9702 15313
235.0
240.0
397.40
0.01861 1.8970 1.9156
372.13 827.9 1200.1
0.5635 0.9661 1.5295
240.0
246.0
399.20
0.01864 1.8589 1.8775
374.09 826.2 12003
0,5658 0.9620 1.5278
245.0
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 8. PROPERTIES OF SATURATED STEAM: PRESSURE TABLE— (Concluded)
Specific Volume
Total Heat
Entropy
AW. Pr*«.
T«rop.
Sat. Sat.
Sat. Sat.
Sat. Sat.
Ab«. Pratt.
Lb.,Sq. In.
D*t> F.
Liquid Evap. Vapor
Liquid Evap. Vapor
Liquid Evap. Vapor
Lb./Sq. In.
P
t
Vf Vf* Vg
hf hfg hg
Sf Sfg Sg
P
260.0
400.97
0.01867 1.8223 1.8410
376.02 824.5 12003
0.5680 0.9581 1.5261
260.0
260.0
404.43
0.01872 1.7536 1.7723
379.78 821.2 1201.0
0.5723 0.9504 1.5227
260.0
270.0
407.79
0.01877 1.6895 1.7083
383.44 818.0 1201.4
0.5765 0.9430 13194
270.0
280.0
411.06
0.01882 1.6302 1.6490
387.02 814.7 1201.8
0.5805 0.9357 1.5163
280.0
290.0
41454
0.01887 1.5745 13934
390.50 811.6 1202.1
0.5845 0.9287 13132
290.0
300.0
41733
0.01892 1.5225 1.5414
393.90 808.5 1202.4
03883 0.9220 13102
300.0
320.0
42359
0.01901 1.4279 1.4469
400.47 8023 1203.0
0.5957 0.9089 1.5046
320.0
340.0
428.96
0.01910 13439 13630
406.75 796.6 1203.4
0.6027 0.8965 1.4992
340.0
360.0
434.39
0.01918 15689 15881
412.80 790.9 1203.7
0.6094 0.8846 1.4940
360.0
380.0
439.59
0.01927 15015 15208
418.61 7853 1203.9
0.6157 0.8733 1.4.891
380.0
400.0
444.58
0.0194 1.1407 1.1601
4245 779.8 1204.1
0.6218 0.8625 1.4843
400.0
420.0
44938
0.0194 1.0853 1.1047
429.6 774.5 1204.1
0.6277 0.8520 1.4798
420.0
440.0
454.01
0.0195 1.0345 1.0540
434.8 7693 1204.1
0.6334 0.8420 1.4753
440.0
460.0
458.48
0.0196 0.9881 1.0077
439.9 764.1 1204.0
0.6388 0.8322 1.4711
460.0
480.0
462.80
0.0197 0.9456 0.9633
444.9 759.0 1203.9
0.6441 0.8228 1.4670
480.0
600.0
466.99
0.0198 0.9063 0.9261
449.7 754.0 1203.7
0.6493 0.8137 1.4630
600.0
620.0
471.05
0.0198 0.8701 0.8899
454.4 749.0 1203.5
0.6543 0.8048 1.4591
520.0
640.0
474.99
0.0199 0.8363 0.8562
459.0 744.1 12035
0.6592 0.7962 1.4554
640.0
660.0
478.82
0.0200 0.8047 0.8247
463.6 7393 1202.9
0.6639 0.7878 1.4517
660.0
680.0
482.55
0.0201 0.7751 0.7952
468.0 734.5 1202.5
0.6686 0.7796 1.4482
680.0
600.0
486.17
0.0202 0.7475 0.7677
4723 729.8 1202.1
0.6731 0.7716 1.4447
600.0
620.0
489.71
0.0202 0.7217 0.7419
476.6 725.1 1201.7
0.6775 0.7638 1.4413
620.0
640.0
493.16
0.0203 0.6972 0.7175
480.8 7203 12015
0.6818 0.7562 1.4380
640.0
660.0
496.53
0.0204 0.6744 0.6948
484.9 715.9 1200.8
0,6861 0.7487 1.4348
660.0
680.0
49932
0.0205 0.6527 0.6732
488.9 7113 12005
0.6902 0.7414 1.4316
680.0
700.0
503.04
0.6206 0.6321 0.6527
492.9 706.8 1199.7
0.6943 0.7342 1.4285
700.0
720.0
506.19
0.0206 0.6128 0.6334
496.8 702.4 11995
0.6983 0.7272 1.4255
720.0
740.0
509.28
0.0207 03944 0.6151
500.6 697.9 1198.6
0.7022 0.7203 1.4225
740.0
760.0
51230
0.0208 0.5769 03977
504.4 693.5 1198.0
0.7060 0.7136 1.4196
760.0
780.0
51557
0.0209 0.5602 03811
5085 689.2 1197.4
0.7098 0.7069 1.4167
780.0
800.0
518.18
0.0209 0.5444 03653
511.8 684.9 1196.7
0.7135 0.7004 1.4139
800.0
820.0
521.03
0.0210 03293 03503
5153 680.6 1196.0
0.7171 0.6940 1.4111
S20.0
840.0
860.0
523.83
526.58
0.0211 03149 0.5360
0.0212 03013 03225
519.0 676.4 1195.4
522.6 672.1 1194.7
0.7207 0.6877 1.4084
0.7242 0.6815 1.4057
840.0
860.0
880.0
52959
0.0213 0.4881 03094
526.0 667.9 1194.0
0.7277 0.6754 1.4031
880.0
900.0
920.0
940.0
960.0
980.0
531.95
534.56
537.13
539.66
542.14
0.0213 0.4756 0.4969
0.0214 0.4635 0.4849
0.0215 0.4520 0.4735
0.0216 0.4409 0.4625
0.0217 0.4303 0.4520
5293 663.8 11933
532.9 659.7 1192.6
5365 655.6 1191.8
539.6 651.5 1191.1
542.8 647.5 11903
0.7311 0.6694 1.4005
0.7344 0.6635 1.3980
0.7377 0.6577 1.3954
0.7410 0.6520 1.3930
0.7442 0.6464 1.3905
900.0
920.0
940.0
960.0
980.0
1000.0
1060.0
1100.0
1160.0
1200.0
544.58
55033
55658
561.81
567.14
0.0217 0.4202 0.4419
0.0219 03960 0,4179
0.0222 03738 03960
0.0224 03540 03764
0.0226 03356 03582
546.0 643.5 1189.6
554.0 633.6 1187.6
561.7 623.9 1185.6
5695 6143 1183.5
576.5 604.9 1181.4
0.7473 0.6408 13881
0.7550 0.6273 13822
0.7624 0.6141 1.3765
0.7695 0.6014 13709
0.7764 03891 13656
1000.0
1060.0
1100.0
1160.0
1200.0
1260.0
1300.0
1360.0
1400.0
1460.0
57230
57732
58251
586.96
591.58
0.0228 03187 03415
0.0230 03029 03259
0.0232 05884 03116
0.0235 05748 05983
0.0237 05621 05858
583.6 595.6 1179.2
590.6 5863 1177.0
597.5 5775 1174.7
6043 568.1 1172.4
•611.0 559.1 1170.0
0.7831 03772 13603
0.7897 03654 13552
0.7962 03540 13501
0.8024 03428 1.3452
0.8086 0.5318 13404
1260.0
1300.0
1360.0
1400.0
1460.0
1500.0
1600.0
1700.0
1800.0
1900.0
5964)8
604.74
612.98
620.86
62839
0.0239 05502 05741
0.0244 05284 05528
0.0249 05089 0.2338
0.0254 0.1913 05167
0.0260 0.1754 05014
617.5 5505 1167.6
6305 532.6 1162.7
6423 515.0 1157.5
654.7 4975 115L8
666.8 478.9 1145.7
0.8146 0:5212 13357
0.8262 0.5003 13265
0.8373 0.4801 13174
0.8482 0.4601 13083
0.8589 0.4402 15990
1600.0
1600.0
1700.0
1800.0
1900.0
ooooo
635.6
6495
661.9
673.8
684.9
0.0265 0.1610 0.1875
0.0277 0.1346 0.1623
0.0292 0.1112 0.1404
0.0310 0.0895 0.1205
0.0333 0.0688 0.1021
679.0 460.0 1139.0
703.7 420.0 1123.8
729.4 376.4 1105.8
756.7 327.8 10843
786.7 2723 1058.9
0.8696 0.4200 15896
0.8912 03788 15700
0.9133 03356 15488
0.9364 05892 15257
0.9618 05379 1.1996
2000.0
2200.0
2400.0
2600.0
2800.0
3000.0
3200.0
3226.0
6955
704.9
706.1
0.0367 0,0477 0.0844
O.C459 0.0142 0.0601
0.0522 0 0.0522
823.1 202.5 1025.6
887.0 75.9 962.9
925.0 0 925.0
0.9922 0.1754 1.1676
1.0461 0.0651 1.1112
1.0785 0 1.0785
3000.0
3200.0
3226.0
- 30
CHAPTER 1. AIR, WATER AND STEAM
responding change in the latent heat of evaporation. These values are
given in Table 8.
Specific Heat. The specific heat of water, or the amount of heat (Btu)
required to raise the temperature of one pound of water one degree Fahren-
heit, varies with the temperature, but it is commonly assumed to be
unity at all temperatures. Steam tables are based on exact values,
however. The specific heat of ice at 32 F is 0.492 Btu per pound. The
amount of heat required to raise one pound of water at 32 F through a
known temperature interval depends on the average specific heat for the
temperature range.
Sensible and Latent Heat. The heat necessary to raise the temperature
of one pound of water from 32 F to the boiling point is known as the heat
of the liquid or sensible heat. When more heat is added, the water begins
to evaporate and expand at constant temperature until the water is
entirely changed into steam. The heat thus added is known as the latent
heat of evaporation.
PROPERTIES OF STEAM
Steam is water vapor which exists in the vaporous condition because
sufficient heat has been added to the water to supply the latent heat of
evaporation and change the liquid into vapor. This change in state takes
place at a definite and constant temperature which is determined solely
by the pressure of the steam. The volume of a pound of steam is the
specific volume which decreases as the pressure increases. The reciprocal
of this, or the weight of steam per cubic foot, is the density. (See Table 8.)
Steam which is in contact with the water from which it was generated is
known as saturated steam. If it contains no actual water in the form of
mist or priming, it is called dry saturated^ steam. If this be heated and the
pressure maintained the same as when it was vaporized, its temperature
will increase and it will become super-heated, that is, its temperature will
be higher than that of saturated steam at the same pressure.
REFERENCES
Temperature of Evaporation, by W. H. Carrier (A.S.H.V.E. TRANSACTIONS, Vol. 24,
1918, p. 25).
The Evaporation of a Liquid into a Gas, by W. K. Lewis (A.S.M.E. Transactions,
Vol. 44, 1922).
The Evaporation of a Liquid into a Gas — a Correction, by W. K. Lewis (Mechanical
Engineering, September, 1933).
Temperature of Evaporation of Water into Air, by W. H. Carrier and D. C. Lindsay
(A.S.M.E. Transactions, Vol. 46, 1924).
A New Psychrometric or Humidity Chart, by C. A. Bulkeley (A.S.H.V.E. TRANS-
ACTIONS, Vol. 32, 1926, p. 163).
A Review of Psychrometric Charts, by C. O. Mackey (Heating and Ventilating,
June, July, 1931).
Air Conditioning Applied to Cold Storage and a New Psychrometric Chart, by C, A.
Bulkeley (Refrigerating Engineering, February, 1932).
The Psychrometric Chart, by E. V. Hill (Aerologist, April, May, June, 1932).
Air Conditioning Theory, by John A. Goff (Refrigerating Engineering, January, 1933).
Mixtures of Air and Water Vapor, by C. A. Bulkeley (Refrigerating Engineering,
January, 1933).
31
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Basic Theory of Air Conditioning, by Lawrence Washington (Western Conference on
Air Conditioning, San Francisco, Calif., February 9-10, 1933).
The Theory of the Psychrometer, by J. H. Arnold (Physics, July, September, 1933).
Heat Transmission in Cooling Air with Extended Surfaces, by W. L. Knaus (Refrigera-
ting Engineering, Januar>T, February, 1935).
A New Psychrometric Chart, by F. 0. Urban (Refrigerating Engineering, November
1935).
Psychrometric Charts, by Donald B. Brooks (U. S. Bureau of Standards Miscellaneous
Publication No. 143).
The Deviation of the Actual Wet-Bulb Temperature from the Temperature of
Adiabatic Saturation, by David Dropkin (Cornell University Engr. Exp. Station Bui.
No. 23, July, 1936).
PROBLEMS IN PRACTICE
1 • Given air at 70 F dry-bulb and 50 per cent relative humidity with a baro-
metric pressure of 29.00 in. Hg, find the weight of vapor per pound of dry air.
Pressure of saturated vapor - et = 0.7387 in. Hg (Table 6).
From Equation 5a,
0.5 X 0.7387 \
- (0.5) X (0.7387)7
W = 0.008024 lb of vapor per pound of dry air at 70 F dry-bulb and 50 per cent
relative humidity.
Approximate Method:
Weight of saturated vapor per pound of dry air = Wt = 0.01574 lb (Table 6). 0.01574
X 0.5 = 0.00787 lb of vapor per pound of dry air at 70 F dry-bulb and 50 per cent relative
humidity.
2 • Given ah- with a dry-bulb temperature of 80 F, relative humidity of 55 per
cent, and a barometric pressure of 28.85 in. Hg, calculate the weight of a cubic
foot of mixture.
Pressure of saturated vapor at 80 F = et = 1.0316 in. Hg (Table 6).
Pressure of the vapor in the mixture - 1.0316 X 0.55 = 0.5676 in. Hg.
Pressure of the dry air in the mixture = 28.85 - 0.5676 = 28.282 in. Hg.
__ 28.282
~ 0.753 X 540 ™ °-06955 lb = weight of dry air in 1 cu ft of the mixture.
Likewise from Equation 4a,
^ = 1.21 X 540 = 0-W0868 lb - weight of vapor per cubic foot at 55 per cent
relative humidity.
Weight of 1 cu ft of the mixture = 0.06955 + 0.000868 = 0.070418 lb. '
3 • Given air with a dry-bulb temperature of 75 F, a relative humidity of 60 per
cent, and a barometric pressure of 28.80 in. Hg, calculate the volume of 1 lb of
ine mixture.
Pressure of saturated vapor at 75 F = et === 0.8745 in. Hg.
Pressure of vapor in the mixture = 0.8745 X 0.6 ~ 0.525 in. Hg.
Pressure of dry air in the mixture « 28.80 - 0.525 - 28.275 in. Hg.
32
CHAPTER 1. AIR, WATER AND STEAM
^ = ______ 28.275 _ = 0.07018 Ib = weight of dry air in 1 cu ft of the mixture.
0.753 X 535
From Equation 4a,
j _ Q*525 _ = 0 000811 Ib = weight of vapor per cubic foot at 55 per cent
** " 1.21 X 535
relative humidity.
Weight of 1 cu ft of the mixture = 0.07018 -f 0.000811 = 0.070991 Ib.
Volume of 1 Ib of the mixture = -Q^ggf = 14-08 cu ft-
4 ® It is desired to maintain a temperature of 80 F and a relative humidity of
^ per cent in a factory where the equipment gives off 6,000 Btu per hour If
th«f entering ah- is at 70 F with an average barometric pressure of 29.92 m. Hg,
determSe the relative humidity, and the pounds of an: required pex -hour *f
there is no heat interchange between the walls, windows, or floors of the
building.
Pressure of saturated vapor at 80 F = 1.0316 in. Hg (Table 6).
Pressure of vapor in the mixture - 1.0316 X 0.5 = 0.5158 in. Hg.
IF = 0-622 ( ^S^ )= 0.01091 Ib.
Pressure of saturated vapor at 70 F « 0,7387 in. Hg.
With the same specific humidity
/ 0.7387 X
0.01091 - 0.622 (29.92 „
$ = 69.8 per cent relative humidity at 70 F. ,
h = 0 24 X 80 + 0.01091 [1059.2 + (0.45 X 80)] = 31.15 Btu per pound, the heat con-
tent of the mixture at 80 F and 50 per cent relative humidity.
h = 0 24 X 70 + 0.01091 [1059.2 + (0.45 X 70)] = 28.70 Btu per pound, the heat con-
tent of the mixture at 70 F and the same specific humidity.
31.15 — 28.70 = 2.45 Btu to be removed per pound of air.
6000 Btu = heat given off by equipment per hour.
6000
2.45
= 2449 Ib of air required per hour.
.
remains constant, what will be the new pressure, P2, in in. Hg?
PV = w£(*
R (for air) = 53.34.
W = 1 Ib.
P = absolute pressure, pounds per square foot.
1 X 53.34 X (78 + 460)
/ " 29.92 X 0.491 X 144
V = 13.57 cu ft = volume of 1 Ib.
P* _ T* p - T*P*
Pi - 3\; 2 Ti
v . (96 + 460) (29.92 X 0.491 X 144) = 3Q M .^ Hg
^2 - (7g + 460) (0.491 X 144)
including the heat content of the liquid above 32 F.
33
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
From Equation 12,
h = 0.24 ft - 0) + Wh+
where
hs « 1059.2 + 0.45*' (Empirical equation derived from Keenan's Steam Tables).
/' = 75 F.
W « 0.01873 Ib of water vapor (Table 6).
h - 0.24 (75 - 0) -f 0.01873 [1059.2 + (0.45 X 75)].
h = 38.46 Btu per pound of dry air.
7 • A building requires 50,000 cu ft of air per hour to be raised from — 10 F
dry-bulb and 75 per cent relative humidity to 72 F dry-bulb and 30 per cent
relative humidity. Determine the amount of heat and the weight of water
which it is necessary to supply per hour if the temperature of the supply water
is 50 F and the barometric pressure is 28.75 in. Hg.
Assume air volume to be dry air at 70 F.
Weight of air « 0.075 X 50,000 - 3750 Ib per hour.
From Table 6,
Pressure of vapor in the mixture, outside air = 0.75 X 0.0221 = 0.0166 in. Hg.
Specific humidity, outside air - 0.622 ( 2g 75° '- cfoiee ) " °-0003589 Ib>
From Table 6,
Pressure of vapor in the mixture, inside air = 0.30 X 0.7906 = 0.2372 in. Hg.
Specific humidity, inside air = 0.622 (2g 75°^ 3Q 237is) = ao05174 lb-
Water to be added = 3750 (0.005174 - 0.0003589 ) = 18.06 lb per hour.
Heat content, inside air = 0.24 X 72 -f 0.005174 [1059.2 + (0.45 X 72)] - 22.925 Btu
per pound.
Heat content, outside air « 0.24 X (-10) -f- 0.0003589 [1059.2 -f (0.45 X -10)] =
-2.021 Btu per pound.
Btu added incident to the water per pound of dry air.
(0.005174 - 0.0003589) (50 - 32) = 0.0867 Btu per pound.
Heat requirement per hour = [22.925 - (-2.021 + 0.0867)] X 3750 = 93,221 Btu.
8 • Determine the amount of heat and water that must be extracted to cool
3750 lb of air (weighed dry) from 95 F and 60 per cent relative humidity to 50 F
and 100 per cent relative humidity with a barometric pressure of 28.75 in. Hg.
Pressure of vapor in the mixture, outside air = 0.6 X 1.659 = 0.995 in. Hg.
Specific humidity, outside air = 0.622 [ no >., ^ Mtf} = 0.0223 lb.
\28.7o — 0.995 /
Specific humidity, inside air - 0.007626 lb.
Weight of water to be extracted per hour = (0.0223 - 0.007626) X 3750 = 55.03 lb.
Heat content, outside air = 0.24 X 95 + 0.0223 [1059.2 -f (0.45 X 95)] - 47.37 Btu
per pound.
Heat content, inside air - 0.24 X 50 -h 0.00764 [1059.2 + (0.45 X 50)] = 20.26 Btu
per pound.
Heat to be extracted = (47.37 - 20.26) X 3750 = 101,662 Btu.
34
Chapter 2
REFRIGERANTS AND AIR DRYING AGENTS
Properties o£ Refrigerant Substances, Selection Fact£r^olid
Adsorbents, Liquid Absorbents, Nature o£ Processes, Tempera-
ture Pressure Concentration Relations
BOTH cooling and dehumidification of air are usually desirable at
certain times. Cooling may be regarded as the extraction of sensible
heat while dehumidification necessitates the removal of patent heat. By
a suitable selection and combination of methods M*^™***^^
processes may be accomplished simultaneously or they ^^6 secured
independent of each other and at different times as desired On occasion
the desired result can be secured by extracting sensible heat only while
in other cases drying alone will produce the end conditions sought.
SuiSble substances must be available for use in every particular case
Generally, when both cooling and dehumidification are fO"^ current
oractice makes use of artificially produced refrigeration in some forrn^
air conditioning work. Little mention is made here °f methods, i y stems
or equipment whereby these substances may be applied, which mtor
mation may be found in Chapter 24.
REFRIGERANTS
Since air cooling and dehumidification are frequently Accomplished by
evaoorating a liquid under circumstances which will permit the neat
necSSrv to be Sracted from the air, the refrigerants are substances
Considerations including availability, cost, safety chemical stability and
adaptability to the type of refrigerating system to be used.
In this chapter detailed consideration is limited to six substances viz
ammonia, carbon dioxide, dichlorodiftuoromethane (P12), methyl
35
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 1. PROPERTIES OF AMMONIA
HEAT CONTENT AND ENTROPY TA.KEN FROM —40 F
T^p< Ln PER Heat Content
t So Is.
Entropy
100 F Superhea
200 F Superheat
i Liquid , Vapor , Liquid
Vapor
Liqui
Vapo
Ht.C
Entro
Ht. C
Entropy
0 , 30.42 0.0241
? 9.116
42
611. i
30.097
1.335
666
1.443
720
1.5317
2 31.92:0.0242
4 8.714
45
612.'
tO. 102
1.331
667
1.440(
721
1.5277
4 j 33 .47,; 0.02430 8.333
47
613. (
)0.106
1.327
668
1.436
722
1.5236
5 34. 27*0.02432 8.150 \ 48
613.;
50.109
1.325
668
1.434
722
1.5216
6 35.09 0.02435 7.971 ! 49
613. <
50.111
1.323
669
1.432
723
1.5196
8 , 36.77 0.02440 7.629
51
614.;
JO. 116
1.319
670
1.428
724
1.5155
10 38.51 0.0244<
S 7.304
53
614. <
J0.120
1.315
670.
1.424
725
1.5115
12 40.3l! 0.0245]
I 6.996
56.
615.*
J0.125
1.311
671.
1.420
725
1.5077
14 42.180.0245'
" 6,703
58.
616.1
0.130C
1.308
672.
1.416
726.
1.5039
16 44.12 0.02462 6.425
60.
616. e
> 0.134
1.304
673.
1.413
727.
1.5001
18
46.13 0.02465
J 6.161
62.
617.2
10.139
1.300
674.
1.409
728.
1 .4963
20
48.2110.02474 5.910
64.
617.
0.143
1.296
675.
1.405
729.
1.4925
22
50.36 0.0247S
> 5.671
66.
618.
0.148
1.293
675.
1.402
730.
1 .4889
24
52.59 0.0248
5.443
69.
618.
0.152
1.289
676.
1.398
731.
1.4853
26
54.90, 0.0249
5.227
71.
619.
0.157
1.286
677.
1.395
732.
1 .4816
28
57.28 0.0249
5.021
73.
619.
0.161
1.282
678.
1.391
733.
1 .4780
30
59.74i 0.0250
4.825
75.
620.
0.166
1.279
678.
1.387
734.
1.4744
32
62.291 0.0250
4.637
77.
621.
0.170
1.275
679.
1.384
735.
1.4710
34
64.91
0.0251
4.459
80.
621.
0.175
1.272
680.
1.381
736.
1.4676
36
67.63
1 0.0252
4.289
82.
622.
0.179
1.268
681.
1.377
736.
1.4643
38
70.4310.0252
4.126
84.
622.
0.184
1.2652
681.
1.374
737.
1.4609
39 71.8710.0253
4.048
85.
622.
0.186
1.2635
682.
1.372
738.
1.4592
40 j 73.32 0.0253
3.971
86.
623.
0.1885
1.2618
682.
1.3712
738.
1.4575
41
74. 80j 0.0253
3.897
87.
623.
0.1908
1.2602
683.
1.3696
739.0
1.4559
42
76.31
0.02539
3.823
89.0
623.4
0.1930
1.2585
683.4
1.3680
739.5
1.4542
44
79.38
0.02545
3.682
91.2
623.9
0.1974
.2552
684.2
1.3648
740 4
.4510
46
82.55
0.0255
3.547
93.5
624.4
0.2018
.2519
684.9
.3616
741.3
.4477
48
85.82
0.02558
3.418
95.7
624.8
0.2062
.2486
685.6
.3584
742 2
.4445
50
89.19
0.02564
3.294
97.9
625.2
0.2105
.2453
686.4
.3552
743.1
.4412
52
92.66
0.02571
3.176
100.2
625.7
0.2149
.2421
687.1
.3521
744.0
!4382
54
96.23
0.02577
3.063
102.4
626.1
0.2192
.2389
687.8
.3491
744.8
.4351
56
99.91
0.02584
2.954
104.7
626.5
0.2236
.2357
688.5
.3460
745.7
.4321
58
103.7
0.02590
2.851
106.9
626.9
0.2279
.2325
689.2
.3430
746 5
4290
60
62
107.6
111.6
0.02597
0.02604
2.751
2.656
109.2
111.5
627.3
627.7
0.2322
0.2365
.2294
.2262
689.9
690.6
.3399
.3370
747.4
748.2
.'4260
4231
66
68
70
72
74
76
78
80
82
84
86
88
90
92
94
96
98
100
102 ;
115.7
120.0
124.3
128.8
133.4
138.1
143.0
147.9
153.0
158.3
163.7
169.2
174.8
180.6
186.6
192.7
198.9
205.3
211.9
218.6
0.02611
0.02618
0.02625
0.02632
0.02639
0.02646
0.02653
0.02661
0.02668
0.02675
0.02684
0.02691
0.02699
0.02707
0.02715
0.02723
0.02731
0.02739
0.02747
0.02756
2.565
2.477
2.393
2.312
2.235
2.161
2.089
2.021
1.955
1.892
1.831
1.772
1.716
1.661
1.609
1.559
1.510
1,464
1.419
1.375
113.7
116.0
118.3
120.5
122.8
125.1
127.4
129.7
132.0
134.3
136.6
138.9
141.2
143.5
145.8
148.2
150.5
152.9
155.2
157.6
628.0
628.4
628.8
629.1
629.4
629.8
630.1
630.4
630.7
631.0
631.3
631.5
631.8
632.0
632.2
632.5
632.6
632.9
633.0
633.2
0.2408
.2451
.2494
.2537
.2579
.2622
.2664
.2706
.2749
.2791
.2833
.2875
.2917
.2958
.3000
.3041
.3083
.3125
.3166
.3207
.2231
.2201
.2170
.2140
.2110
2080
2050
2020
1991
1962
1933
1904
1875
1846
1818
1789
1761
1733
1705
1677
691.3
691.9
692.6
693.3
694.0
694.6
695.3
695.9
696.6
697.2
697.8
698.5
99.1
99.7
00.3
00.9
01.5
02.1
02.7
03.3
.3341
.3312
.3283
.3254
.3226
.3199
.3171
.3144
.3116
.3089
3063
3040
3010
2983
2957
2932
2906
2881
2855
2830
749.1
749.9
750.8
751.6
752.4
753.3
754.1
755.0
755.8
756.6
757.4
758.3
759.1
759.9
760.7
61.5
62.2
63.0
63.8
64.6
.4202
.4172
.4143
.4114
.4086
.4059
.4031
.4004
3976
3949
3923
3896
3870
3843
3818
3793
3768
3743
3718
3693
36
CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS
TABLE 1. PROPERTIES OF AMMONIA— (Continued)
HEAT CONTENT AND ENTROPY TAKEN FROM -40 F
o.m
ABB
.»
oAT.
TEMP.
F
PRESS.
LB PER
SQlN.
V OLUME
Heat Content
Entropy
100 F Superheat
200 F Superheat
Liquid
Vapor
Liquid
Vapor
Liquid
Vapor
Ht. Ct.
Entropy
Ht. Ct.
Entropy
104
225.4
0.0276*
1.334
159.9
633.4
0.3248
1.1649
703.8
1.2805
765.3
1.3668
106
232.5
0.02773
1.293
162.3
633.5
0.3289
1.1621
701.3
1.2780
766.1
1.3643
108
239.7
0.02782
1.254
164.6
633.6
0.3330
1.1593
705.0
1.2755
766.9
1.3619
110
247.0
0.02790
1.217
167.0
633.7
0.3372
1.1566
705.5
.2731
767.6
1.3596
112
254.5
0.02799
1.180
169.4
633.8
0.3413
1.1538
706.1
.2708
768.3
1.3573
114
262.2
0.02808
1.145
171.8
633.9
0.3453
1.1510
706.6
.2684
769.1
1.3550
116
270.1
0.02817
1.112
174.2
634.0
0.3495
1.1483
707.2
.2661
769.8
1.3527
118
278.2
0.02827
1.079
176.6
634.0
0.3535
1.1455
707.7
.2636
770.5
1.3503
120
286.4
0.02836
1.047
179.0
634 0
0.3576
1.1427
708.2
.2612
771.3
1.3479
122
294.8
0.02846
1.017
181.4
634.0
0.3618
1.1400
708.6
.2587
772.0
1.3455
124
303.4
0.02855
0.987
183.9
634.0
0.3659
1.1372
709.1
.2563
772.8
1.3431
126
312.2
0.02865
0.958
186.3
633.9
0.3700
1.1344
709.6
1.2538
773.5
1.3407
128
321.2
0.02875
0.931
188.8
633.9
0.3741
1.1316
710.0
1.2513
774.2
1.3383
chloride, water, and monofluorotrichloromethane (Fn), for each of
which a tabl.e is presented. Each table gives the principal physical
properties of the saturated substance,, and all are arranged in uniform
fashion. In each case columns are included which give the heat content
and entropy of the superheated vapor at two selected points. Tables 1,
2, 3 and 4 which include the refrigerants much used in reciprocating and
rotary mechanical compression systems have a 2 F temperature interval.
As water and JPu are much used in centrifugal compression systems the
temperature interval in Tables 5 and 6 is 5 F.
AIR DRYING AGENTS
Moisture may be removed from air, thus accomplishing dehumidi-
fication, by the use of any one of a number of substances if the moist air
and these substances are brought together under suitable circumstances.
One class of these substances are solids at ordinary conditions and have
the power of adsorbing the moisture from the air. Another class of air
drying agents are liquids under ordinary conditions and absorb the mois-
ture from the air. Nearly all the drying agents in frequent commercial
use in air conditioning installations are of one or the other of these two
classes.
Adsorbents
These substances are characterized by a physical structure containing
a great number of extremely small pores but still retaining sufficient
mechanical strength to resist whatever wear and handling to which they
are subjected. To be suitable for air drying purposes they must be widely
available at economical cost, durable in use, stable in form and properties,
and capable of withstanding the re-activation processes by which they are
made ready for repeated use. They must also possess capacity for
adsorbing and holding so sufficient a quantity of moisture that the
dimensions of the beds necessary to accommodate them will be practical.
37
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2, PROPERTIES OF CARBON DIOXIDE
HEAT CONTENT AND ENTROPY TAKEN FROM —40 F
& p*--
^' LB PER
* SQ Is.
VOLUME
Heat Content
Entropy
50 F Superheat
100 F Superheat
Liquid Vapor
Liquid
1
Vapor
Liquid
Vapor
Ht. Ct.
Entropy
Ht. Ct.
Entropy
0
305.5 0.01570 0.29040
18.8
138.9
0.0418
0.3024
153.7
0.3342
167.5
0.3612
315.9
0.01579 0.28030
19.8
138.8
0.0440
0.3014
153.7
0.3330
167.6
0.3600
4
326.5
0.01588 0.27070
20.8
138.8
0.0461
0.3005
153.7
0.3318
167.7
0.3588
5
332.0
0.0159210.26610
21.3
138.8
0.0472
0.3000
153.7
0.3312
167.7
0.3582
6
337.4
0.01596
0.26140
21.8
138.7
0.0483
0.2994
153.7
0.3306
167.8
0.3576
8
348.7
0.01605
0.25260
22.9
138.7
0.0504
0.2982
153.7
0.3293
167.9
0.3563
10
360.2
0.01614
0.24370
24.0
138.7
0.0526
0.2970
153.7
0.3281
168.0
0.3550
12
371.9
0.01623
0.23540
25.0
138.6
0.0548
0.2958
153.7
0.3270
168.1
0.3538
14
383.9
0.01632
0.22740
26.1
138.6
0.0571
0.2946
153.7
0.3259
168.2
0,3526
16
396.2
0.01642
0.21970
27.2
138.5
0.0593
0.2933
153.7
0.3249
168.3
0.3513
18
408.9
0.01652
0.21210
28.3
138.4
0.0616
0.2921
153.7
0.3238
168.5
0.3501
20
421.8
0.01663
0.20490
29.4
138.3
0.0638
0.2909
153.7
0.3227
168.6
0.3489
22
434.0
0.01673
0.19790
30.5
138.2
0.0662
0.2897
153.7
0.3214
168.7
0.3479
24
448.410.01684
0.19120
31.7
138.1
0.0686
0.2885
153.7
0.3202
168.8
0.3470
26
462.2
0.01695
0.18460
32.9
138.0
0.0710
0.2873
153.7
0.3189
168.9
0.3460
28
476.3
0.01707
0.17830
34.1
137.9
0.0734
0.2861
153.7
0.3177
169.0
0.3451
30
490.8
0.01719
0.17220
35.4
137.8
0.0758
0.2849
153.7
0.3164
169.1
0.3441
32
505.5
0.01731
0.16630
36.7
137.7
0.0781
0.2834
153.7
0.3158
169.2
0.3431
34
522.6
0.01744
0.16030
37.9
137.4
0.0804
0.2820
153.7
0.3151
169.3
0.3421
36
536.0
0.01759
0.15500
39.1
137.2
0.0828
0.2805
153.7
0.3145
169.4
0.3411
38
551.7
0.01773
0.14960
40.4
136.9
0.0851
0.2791
153.7
0.3138
169.5
0.3401
39
559.7
0.01780
0.14700
41.0
136.8
0.0862
0.2783
153.7
0.3135
169.5
0.3396
40 i 567.8
0.01787
0.14440
41.7
136.7
0.0874
0.2776
153.7
0.3132
169.6
0.3391
41
576.0
0.01794
0.14185
42.3
136.5
0.0887
0.2768
153.7
0.3127
169.6
0.3386
42
584.3
0.01801
0.13930
42.9
136.3
0.0899
0.2761
153.7
0.3122
169.7
0.3381
44
601.1
0.01817
0.13440
44.3
136.1
0.0924
0.2745
153.7
0.3112
169.8
0.3371
46
618.2
0.01834
0.12970
45.6
135.7
0.0950
0.2730
153.7
0.3101
169.9
0.3362
48
635.710.01851
0.12500
47.0
135.4
0.0975
0.2714
153.7
0.3091
170.0
0.3352
50
653.6
0.01868
0.12050
48.4
135.0
0.1000
0.2699
153.7
0.3081
170.1
0.3342
52
671.9
0.01887
0.11610
49.8
134.5
0.1027
0.2681
153.7
0.3069
170.2
0.3333
54
690.6
0.01906
0.11170
51.2
133.9
0.1054
0.2663
153.7
0.3057
170.3
0.3324
56
709.5
0.01927
0.10750
52.6
133.4
0.1081
0.2644
153.7
0.3046
170.5
0.3315
58
728.8
0.01948
0.10340
54.0
132.7
0.1108
0.2626
153.7
0.3034
170.6
0.3306
60
748.6
0.01970
0.09940
55.5
132.1
0.1135
0.2608
153.7
0.3022
170.7
0.3297
62
769.0
0.01995
0.09545
57.0
131.3
0.1164
0.2584
153.7
0.3012
170.8
0.3289
64
789.4
0.02020
0.09180
58.6
130.6
0.1194
0.2560
153.7
0.3002
170.9
0.3281
66
810.3
0.02048
0.08800
60.2
129.7
0.1223
0.2535
153.7
0.2991
171.0
0.3273
68
831.6
0.02079
0.08422
61.9
128.7
0.1253
0.2511
153.7
0.2981
171.1
0.3265
70
853.4
0.02112
0.08040
63.7
127.5
0.1282
0.2487
153.7
0.2971
171.2
0.3257
72
875.8
0.02152
0.07654
65.5
126.0
0.1321
0.2450
153.7
0.2962
171.3
0.3250
74
898.2
0.02192
0.07269
67.3
124.5
0.1360
0.2414
153.7
0.2953
171.4
0.3242
76
921.3
0.02242
0.06875
69.4
122.8
0.1398
0.2377
153.7
0.2945
171.5
0.3235
78
944.8
0.02300
0.06473
71.6
120.9
0.1437
0.2341
153.7
0.2936
171.6
0.3227
80
968.7
0.02370
0.06064
73.9
118.7
0.1476
0.2304
153.7
0.2927
171.7
0.3220
82
993.0
0.02456
0.05648
76.4
116.6
0.1578
0.2195
153.7
0.2920
173.8
0.3215
84
1017.7
0.02553
0.05223
79.4
113.9
0.1679
0.2087
153.7
0.2914
176.0
0.3209
86
1043.0
0.02686
0.04789
83.3
110.4
0.1781
0.1978
153.7
0.2907
178.2
0.3204
87.8
1069.9
0.03454
0.03454
97.0
97.0
0.1880
0.1880
153.7
0.2901
180.1
0.3199
CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS
Aluminum Oxide, (Alumina), in a porous, amorphous form is a solid
adsorbent frequently called by the common name activated alumina, and
containing small amounts of hydrated aluminum oxide, and very small
amounts of soda, and various metallic oxides. A good grade of activated
alumina will show 92 per cent of AkOz, and its soda content will be com-
bined with silica and alumina into an insoluble compound. This substance
also has the property of adsorbing certain gases and certain vapors other
"80 I2D 160 200"
ENTERING AIR TEMPERATURE, °F
FIG. 1. TEMPERATURE— VAPOR PRESSURE— CONCENTRATION RELATION FOR A
SILICA GEL BED AT CONSTANT TEMPERATURE
than water vapor— a property which is sometimes useful in air condi-
tioning installations. It is available commercially in granules ranging
trom a fine powder to pieces approximately 1.5 in. in diameter. It has
iiigh adsorptive capacity per unit of weight, and is non-toxic. It may be
repeatedly re-activated after becoming saturated with adsorbed moisture
without practical loss of its adsorptive ability. In the grade frequently
US!i °or^dTng £e re-activati<>n may be accomplished at temperatures
under 350 F. Specific gravity is 3.25 and the pores are reported to occupy
58 per cent of the volume of each particle. For most estimating purposes
39
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 3. PROPERTIES OF DICHLORODIFLUOROMETHANE(FIO)
HEAT CONTENT AND ENTROPY TAKEN FROM -40 F
rlS; *•*
T|SP' LBMB
h SQ!N.
VOLUME
1 Heat Content
Entropy
25 F Superheat
50 F Superheat
Liquid Vapor Uquid 1 Vapor
Liquid
Vapor
Ht. Ct.
Entropy
Ht. Ct.
Entropy
0 i 23.870.0110J 1.637 8.25
78.21
0.01869
0.17091
81.71
0.17829
85.26
0.18547
2 24 890.01101 1.5741 8.67
78.44
0.01961
0.17075
81.94
0.17812
85.51
0.18529
4
25.960.0111 1.514 9.10
i 78.67
0.02052
0.17060
82.17
0.17795
85.76
0.18511
5 26. 510.0111! 1.485! 9.32 78.79
0.02097
0.17052
82.29
0.17786
85.89
0.18502
6 ! 27.050.0111 1.457
9.53
78.90
0.02143
0.17045
82.41
0.17778
86.01
0.18494
8 ' 28.180.0111J 1.403 9.96
79.13
0.02235
0.17030
82.66
0.17763
86.26
0.18477
10 : 29.350.0112 1.3511 10.39
79.36
0.02328
0.17015
82.90
0.17747
86.51
0.18460
12 ; 30.560.0112 1.301
10.82
79.59
0.02419
0.17001
83.14
0.17,733
86.76
0.18444
14 31.800.0112 1.253
11.26
79.82
0.02510
0.16987
83.38
0.17720
87.01
0.18429
16 ! 33.0810. 0112
1.207
11.70
80.05
0.02601
0.16974
83.61
0.17706
87.26
0.18413
18 j 34.400.01131 1.163
12.12
80.27
0.02692
0.16961
83.85
0.17693
87.51
0.18397
20 35. 75 0.0113| 1.121
12.55
80.49
0.02783
0.16949
84.09
0.17679
87.76
0.18382
22 ! 37.150.0113 1.081
13.00
80.72
0.02873
0.16938
84.32
0.17666
88.00
0.18369
24 38.580.0113
1.043
13.44
80.95
0.02963
0.16926
84.55
0.17652
88.24
0.18355
26 40.070.0114
1.007
13.88
81.17
0.03053
0.16913
84.79
0.17639
88.49
0.18342
28 41.590.0114
0.973
14.32
81.39
0.03143
0.16900
85.02
0.17625
88.73
0.18328
30
43.160.0115
0.939
14.76
81.61
0.03233
0.16887
85.25
0.17612
88.97
0.18315
32
44.77
0.0115
0.908
15.21
81.83
0.03323
0.16876
85.48
0.17600
89.21
0.18303
34
46.420.0115
0.877
15.65
82.05
0.03413
0.16865
85.71
0.17589
89.45
0.18291
36 48. 13)0.0116
0.848
16.10
82.27
0.03502
0.16854
85.95
0.17577
89.68
0.18280
38 49.88^0.0116
0.819
16.55
82.49
0.03591
0.16843
86.18
0.17566
89.92
0.18268
39 50.780.0116
0.806
16.77
82.60
0.03635
0.16838
86-29
0.17560
90.04
0.18262
40 ; 51.680.0116
0.792
17.00
82.71
0.03680
0.16833
86.41
0.17554
90.16
0.18256
41 ; 52.70:0.0116
0.779
17.23
82.82
0.03725
0.16828
86.52
0.17549
90.28
0.18251
42 53.510.0116
0.767
17.46
82.93
0.03770
0.16823
86.64
0.17544
90.40
0.18245
44
55.40)0.0117
0.742
17.91
83.15
0.03859
0.16813
86.86
0.17534
90.65
0.18235
46
57.35
0.0117
0.718
18.36
83.36
0.03948
0.16803
87.09
0.17525
90.89
0.18224
48
59.35
0.0117
0.695
18.82
83.57
0.04037
0.16794
87.31
0.17515
91.14
0.18214
50
61.390.0118 0.673
19.27
83.78
0.04126
0.16785
87.54
0.17505
91.38
0.18203
52
63.49
0.0118
0.652
19.72
83.99
0.04215
0.16776
87.76
0.17496
91.61
0.18193
54
65.63jO.0118
0.632
20.18
84.20
0.04304
0.16767
87.98
0.17486
91.83
0.18184
56
67.8410. 0119
0.612
20.64
84.41
0.04392
0.16758
88.20
0.17477
92.06
0.18174
58
70.100.0119
0.593
21.11
84.62
0.04480
0.16749
88.42
0.17467
92.28
0.18165
60 72.41jO.0119
0.575
21.57
84.82
0.04568
0.16741
88.64
0.17458
92.51
0.18155
62 i 74.77
0.0120
0.557
22.03
85.02
0.04657
0.16733
88.86
0.17450
92.74
0.18147
fri
77.20
0.0120
0.540
22.49
85.22
0.04745
0.16725
89.07
0.17442
92.97
0.18139
66 79.67
0.0120
0.524
22.95
85.42
0.04833
0.16717
89.29
0.17433
93.20
0.18130
68 82.24
0.0121
0.508
23.42
85.62
0.04921
0.16709
89.50
0.17425
93.43
0.18122
70
84.82
0.0121
0.493
23.90
85.82
0.05009
0.16701
89.72
0.17417
93.66
0.18114
72 ! 87.50
0.0121
0.479
24.37
86.02
0.05097
0.16693
89.93
0.17409
93.99
0.18106
74 90.20
0.0122
0.464
24.84
86.22
0.05185
0.16685
90.14
0.17402
94.12
0.18098
76 93.00
0.0122
0.451
25.32
86.42
0.05272
0.16677
90.36
0.17394
94.34
0.18091
78 95.85
0.0123
0.438
25.80
86.61
0.05359
0.16669
90.57
0.17387
94.57
0.18083
80 98.76
0.0123
0.425
26.28
86.80
0.05446
0.16662
90.78
0.17379
94.80
0.18075
82 1101.70
0.0123
0.413
26.76
86.99
0.05534
0.16655
90.98
0.17372
95.01
0.18068
84 il04.S
0.0124
0.401
27.24
87.18
0.05621
0.16648
91.18
0.17365
95.22
0.18061
86 i!07.9
0.0124
0.389
27.72
87.37
0.05708
0.16640
91.37
0.17358
95.44
0.18054
88
111,1
0.0124
0.378
28.21
87.56
0.05795
0.16632
91.57
0.17351
95.65
0.18047
90
114.3
0.0125
0.368
28.70
87.74
0.05882
0.16624
91.77
0.17344
95.86
0.18040
92
117.7
0.0125 0.357
29.19
87.92
0.05969
0.16616
91.97
0.17337
96.07
0.18033
94
121.0
0.0126 0.347
29.68
88.10
0.06056
0.16608
92.16
0.17330
96.28
0.18026
96
124.5
0.0126
0.338
30.18
88.28
0.06143
0.16600
92.36
0.17322
96 50
0.18018
98 128.0
0.0126
0.328
30.67
88.45
0.06230
0.16592
92.55
0.17315
96.71
0.18011
100 J131.6
0.0127
0.319
31.16
88.62
0.06316
0.16584
92.75
0.17308
96.92
0 18004
102
135.3
0.0127
0.310
31.65
88.79
0.06403
0.16576
92.93
0.17301
97.12
0.17998
40
CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS
TABLE 3. PROPERTIES OF DICHLORODIFLUOROMETHANE (Fi2) — Continued
SAT.
TEMP.
F
ABS
PRESS.
LB PER
SQ!N.
VOLUME
HEAT CONTENT AND ENTROPY TAKEN FBOM —40 F
Heat Content
Entropy
25 F Superheat
SO F Superheat
Liquid
Vapor
Liquid
Vapor
Liquid
Vapor
Ht. Ct.
Entropy
Ht Ct.
Entropy
104
139.0
0.0128
0.302
32.15
88.95
0.06490
0.16568
93.11
0.17294
97.32
0.17993
106
142.8
0.0128
0.293
32.65
89.11
0.06577
0.16560
93.30
0.17288
97.53
0.17987
108
146.8
0.0129
0.285
33.15
89.27
0.06663
0.16551
93.48
0.17281
97.73
0.17982
110
150.7
0.0129
0.277
33.65
89.43
0.06749
0.16542
93.66
0.17274
97.93
0.17976
112
154.8
0.0130
0.269
34.15
89.58
0.06836
0.16533
93.82
0.17266
98.11
0.17969
114
158.9
0.0130
0.262
34.65
89.73
0.06922
0.16524
93.98
0.17258
98.29
0.17961
116
163.1
0.0131
0 254
35.15
89.87
0.07008
0.16515
94.15
0.17249
98.4810.17954
118
167.4
0.0131
0.247
35.65
90.01
0.07094
0.16505
94.31
0.17241
98.66
0.17946
120
171.8
0.0132
0.240
36.16
90.15
0.07180
0.16495
94.47
0.17233
98.84
0.17939
122
176.2
0.0132
0.233
36.66
90.28
0.07266
0.16484
94.63
0.17224
99.01
0.17931
124
180.8
0.0133
0.227
37.16
90.40
0.07352
0.16473
94.78
0.17215
99.18
0.17922-
126
185.4
0.0133
0.220
37.67
90.52
0.07437
0.16462
94.94
0.17206
99.35
0.17914
128
190.1
0.0134
0.214
38.18
90.64
0.07522
0.16450
95.09
0.17196
99.53
0.17906
130
194.9
0.0134
0.208
38.69
90.76
0.07607
0.16438
95.25
0.17186
99.70
0.17897
132
199.8
0.0135
0.202
39.19
90.86
0.07691
0.16425
95.41
0.17176
99.87
0.17889
134
204.8
0.0135
0.196
39.70
90.96
0.07775
0.16411
95.56
0.17166
100.04
0.17881
136
209.9
0.0136
0.191
40.21
91.06
0.07858
0.16396
95.72
0.17156
100.22
0.17873
138
215.0
0.0137
0.185
40.72
91.15
0.07941
0.16380
95.87
0.17145
100.39
0.17864
140
220.2
0.0138
0.180
41.24
91.24
0.08024
0.16363
96.03
0.17134
100.56
0.17856
the volume-weight relation on a dry basis may be taken as 50 Ib per cubic
foot although in the smaller sizes the packed weight may be as much as
64 Ib per cubic foot.
Silicon Dioxide, (Silica), in a special form obtained by suitably mixing
sulphuric acid with sodium silicate, is another solid adsorbent and is
commonly called silica gel. Its capillary structure is exceedingly small,
so small that its exact structure has to be deduced rather than observed.
The gel is available commercially in a wide variety of sizes of granules
ranging from 4 to 300 mesh. It has high adsorptive capacity per unit
of weight and is non-toxic, may be repeatedly re-activated without
practical deterioration. Re-activation may be accomplished at tem-
peratures of air up to 600 F although it is frequently accomplished with
air or other gases at temperatures not over 350 F. Volume of the capillary
pores is reported to be from 50 to 70 per cent of the total solid volume.
For most estimating purposes the volume-weight relation can be assumed
as from 38 to 40 Ib per cubic foot on a dry basis.
Other substances having properties which make them available as
solid adsorbents include lamisilate and charcoal but details of their
physical properties are not available.
Nature of Adsorption Process
Adsorption is accomplished without chemical change between the air
and the adsorbent substance. The adsorbent does not go into solution but
water vapor is extracted from the air-vapor stream passing through the
bed of adsorbent material and is caught and retained in the capillary
pores. The exact nature of the process which goes on during adsorption
41
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 4. PROPERTIES OF METHYL CHLORIDE
HEAT CONTEST AND ENTROPY TAKEN FROM -40 F
F SslN?
I
VoL-nos •
I Heat Content ' Entropy
100 F Superheat
200 F Superheat
Liquid ;' Vapor Liquid Vapor
Liquid
Vapor
Ht. Ct.
Entropy
Ht. Ct.
Entropy
0 18.73 0.0162 : 5.052 14,4 192.4
0.0328
0.4197
215.6
0.467
237.2
0.507
2 19.60 0.0162 4.856 15.1 i 193.1
0.0344
0.4196
216.2
0.466
237.7
0.505
4 I 20.47 0.0163 , 4.661 15.8
193.80.0360
0.4195
216.7
0.465
238.2
0.504
5 i 20.91:0.0163
4.563 16.2
194.1
0.0368
0.4195
217.0
0.464
238.5
0.503
6
21. 39; 0.0163 4.476 16.6
194.4
0.0376
0.4194
217.3
0.464
238.8
0.502
8
22. 34' 0.0164
4.303 17.3
195.1
0.0391
0.4193
217.9
0.463
239.4
0.501
10
23.30 0.0164
4.129 18.1
195.8
0.0407
0.4192
218.5
0.463
240.0
0.500
12
24.38 0.0164 ' 3.984 18.8
196.3
0.0423
0.4184
219.0
0.462
240.5
0.499
14
25.46 0.0164 3.839 19.6
196.7
0.0439
0.4176
219.5
0.462
241.0
0.498
16
26.55 0,0165 3.693
20.3
197.2
0.0454
0.4168
220.0
0.461
241.5
0.498
18
27. 63' 0.0165
3.548
21.1
197.6
0.0472
0.4160
220.5
0.461
242.0
0.497
20
28. 71! 0.0166
3.403
21.8
198.1
0.0486
0.4152
221.0
0.460
242.5
0.496
22
29.98 0.0166
3.288
22.5
198.5
0.0501
0.4148
221.5
0.459
243.0
0.495
24
31.25 0.0166
3.172
23.3
198.9
0.0516
0.4143
222.0
0.459
243.6
0.495
26
32.53 0.0167
3.057
24.0
199.3
0.0532
0.4139
222.4
0.458
244.1
0.494
28
33. 801 0.0167
2.941
24.8
199.7
0.0547
0.4134
222.9
0.458
244.7
0.494
30
35. 0/1 0.0168
2.826
25.5
200.1
0.0562
0.4130
223.4
0.457
245.2
0.493
32 36.55
0.0168
2.734
26.2
200.5
0.0577
0.4124
223.9
0.456
245.7
0.492
34
38.03 0.0169
2.642
27.0
200.9
0.0592
0.4118
224.3
0.455
246.2
0.492
36
39.5110.0169
2.549
27.7
201.4
0.0607
0.4111
224.8
0.455
246.7
0.491
38
40.99
0.0169
2.457
28.5
201.8
0.0622
0.4105
225.2
0.454
247.2
0.491
39
41.73
0.0170
2.411
28.8
202.0
0.0629
0.4102
225.5
0.453
247.4
0.490
40
42.47
0.0170
2.365
29.2
202.2
0.0637
0.4099
225.7
0.453
247.7
0.490
41
43.33
0.0170
2.328
29.6
202.4
0.0644
0.4096
225.9
0.453
248.0
0.490
42
44.18
0.0171
2.290
29.9
202.6
0.0651
0.4093
226.1
0.452
248.3
0.489
44
45.89
0.0171
2.216
30.7
203.0
0.0666
0.4087
226.6
0.451
248.8
0.489
46
47.61
0.0171
2.141
31.4
203.3
0.0680
0.4081
227.0
0.451
249.4
0.488
48
49.32
0.0172
2.067
32.2
203.7
0.0695
0.4075
227.5
0.450
249.9
0.488
50
51.03
0.0172
1.992
32.9
204.1
0.0709
0.4069
227.9
0.449
250.5
0.487
52
53.00
0.0172
1.931
33.7
204.4
0.0724
0.4063
228.2
0.448
251.0
0.486
54
54.97
0.0173
1.870
34.4
204.7
0.0739
0.4056
228.6
0.448
251.5
0.486
56
56.94
0.0173
1.810
35.2
205.1
0.0754
0.4050
228.9
0.447
252.0
0.485
58
58.91
0.0173
1.749
35.9
205.4
0.0769
0.4043
229.3
0.447
252.5
0.485
60
60.88
0.0174
1.688
36.7
205.7
0.0784
0.4037
229.6
0.446
253.0
0.484
62
63.13
0.0174
1.638
37.4
206.0
0.0798
0.4030
229.9
0.445
253.5
0.483
64
65.37
0.0174
1.588
38.2
206.3
0.0812
0.4024
230.3
0.444
254.0
0.483
66
67.62
0.0175
1.539
38.9
206.6
0.0827
0.4017
230.6
0.443
254.5
0.482
68
69.86
0.0175
1.489
39.7
206.9
0.0841
0.4011
231.0
0.442
255.0
0.482
70
72.11
0.0176
1.439
40.4
207.2
0.0855
0.4004
231.3
0.441
255.5
0.481
72
74.66
0.0176
1.398
41.1
207.5
0.0869
0.3998
231.6
0.440
256.0
0.480
74
77.21
0.0177
1.357
41.9
207.7
0.0883
0.3992
232.0
0.439
256,5
0.480
76
79.76
0.0177
1.315
42.6
208.0
0.0898
0.3985
232.3
0.439
256.9
0.479
78
82.31
0.0178
1.274
43.4
208.2
0.0912
0.3979
232.7
0.438
257.4
0.479
80
84.86
0.0178
1.233
44.1
208.5
0.0926
0.3973
233.0
0.437
257.9
0.478
82
87.74
0.0178
1.199
44.8
208.7
0.0940
0.3967
233.3
0.436
258.4
0.478
84
90.62
0.0179
1.165
45.6
209.0
0.0953
0.3960
233.6
0.435
258.9
0.477
86
93.50
0.0179
1.130
46.3
209.2
0.0967
0.3954
233.9
0.435
259.4
0.477
88
96.38
0.0180
1.096
47.1
209.5
0.0980
0.3947
234.2
0.434
259.9
0.476
90
99.26
0.0180
1.062
47.8
209.7
0.0994
0.3941
234.5
0.433
260.4
0.476
92
102.49
0.0180
1.033
48.6
209.9
0.1008
0.3935
234.8
0.433
260.8
0.476
94
105.72
0.0181
1.005
49.3
210.2
0.1022
0.3929
235.1
0.432
261.2
0.475
96
108.94
0.0181
0.9764
50.1
210.4
0.1035
0.3922
235.4
0.432
261.6
0.475
98
112.17
0.0182
0.9478
50.8
210.7
0.1049
0.3916
235.7
0.431
262 0
0.474
100
115.40
0.0182
0.9193
51.6
210.9
0.1063
0.3910
236.0
0.431
262.4
0^474
102
119.00
0.0183
0.8952
52.3
211.1
0.1076
0.3903
236.4
0.430
262.8
0.474
42
CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS
TABLE 4. PROPERTIES OF METHYL CHLORIDE — (Continued)
HEAT CONTENT AND ENTBOPY TAKES FBOJI — 40 F
O.m
ABS
VOTTTMTS
TEMP.
F
PRESS.
LB PER
SQ IN.
Heat Content
Entropy
100 F Superheat
200 F Superheat
Liquid
Vapor
Liquid
Vapor
Liquid
Vapor
Ht. Ct.
Entropy
HtCt
Entropy
104
122.60
0.0183
0.8712
53.1
211.3
0.1090
0.3897
236.8
0.430
263.2
0.473
106
126.20
0.0184
0.8471
53.8
211.4
0.1103
0.3890
237.1
0.429
263.5
0.473
108
129.80
0.0184
0.8231
54.6
211.6
0.1117
0.3884
237.5
0.429
263.9
0.472
110
133.40
0.0185
0.7990
55.3
211.8
0.1130
0.3877
237.9
0.428
264.3
0.472
112
137.42
0.0185
0.7786
56.1
212.0
0.1144
0.3871
238.1
0.427
264.6
0.471
114
141.44
0.0185
0.7583
56.8
212.2
0.1157
0.3864
238.3
0.427
264.8
0.470
116
145.46
0.0186
0.7379
57.6
212.4
0.1171
0.3858
238.6
0.426
265.1
0.470
118
149.48
0.0186
0.7176
58.3
212.6
0.1184
0.3851
238.8
0.426
265.3
0.469
120
153.50
0.0187
0.6972
59.1
212.8
0.1198
0.3845
239.0
0.425
265.6
0.468
is not known but it is stated that the action is brought about by surface
condensation, and also by a difference between the vapor pressure of the
water condensing inside the pores and the partial pressure of the water
vapor in the air-vapor mixture. The adsorbing process in the bed can
continue until the vapor pressures come into equilibrium. The amount
of vapor adsorbed will depend on the adsorbent substances being used
but for any single substance the amount depends on the temperature of
the bed as well as on the partial pressure of the air-vapor mixture being
passed over it.
As the process of adsorption goes on heat is liberated in the bed. The
heat so liberated is the latent heat of the water vapor condensed together
with the so-called heat of wetting. For a pound of water vapor at 60 F
the latent heat released by condensation is approximately 1057 Btu.
The heat of wetting for silica gel, for example, is about 200 Btu, making a
total heat of adsorption of approximately 1257 Btu per pound of water
adsorbed from the air-vapor mixture passing through the silica gel bed.
The heat of wetting varies with the substance being used as the adsorbent
while the latent heat of condensation depends only on the temperature
and pressure of the water vapor.
Temperature-Pressure-Concentration Relations
Since the adsorptive ability of an adsorbent depends on the temperature
of the bed and on the partial pressure difference between the pores and the
air-vapor mixture it is important to know the pressures and temperatures
at which pressure equilibrium is reached.
Evidently the equilibrium conditions represent the limits beyond
which adsorption of vapor cannot continue. The relationship can be
shown graphically and Fig. 1 is such a chart for silica gel. Charts of like
nature can be plotted for other adsorbent materials.
Fig, 1 shows the equilibrium conditions for a gel bed maintained at
constant temperature while the water vapor adsorption is allowed to
continue until pressure equilibrium is reached. Each curve on the chart
show a certain dew-point temperature, and therefore a certain pressure,
of the saturated water vapor.
43
HEATING VENTILATING . AIR CONDITIONING GUIDE 1938
TABLE 5. PROPERTIES OF MONOFLUOROTRICHLOROMETHANE (Fn)
SAT.
Tin*.
F
ABS
PRKS.
LB PIE
Sal*.
i VOLUME
MTCAT UONCTNT AND .ttNTBOPY TAKEN i? BOM —40 JB
i Heat Content
Entropy
25 F Superheat
SO F Superheat
; Liquid j Vapor ! Liquid Vapor
Liquid
Vapor
Ht. Ct.
Entropy
Ht. Ct.
Entropy
0
2. 59J 0.01020! 13. 700
7.81
90.4
0.0178
0.1975
93.9
0.2049
97.4
0.2120
5 ; 2.9610.01024S12.100
8.81
91.2
0.0200
0.1974
94.7
0.2047
98.2
0.2117
10 : 3. 38 i 0.01028! 10.700
9.82
92.0
0.0222
0.1973
95.5
0.2045
99.0
0.2114
15
3.85
0.010321 9.530
10.80
92.8
0.0243
0.1971
96.3
0.2043
99.8
0.2111
20
4.3610.01036! 8.490
11.90
93.7
0.0264
0.1970
97.2
0.2041
100.7
0.2109
25
4.94
0.01040
7.580
12.90
94.5
0.0286
0.1969
98.0
0.2039
101.5
0.2107
30
5.57
0.01045
6.770
13.90
95.3
0.0307
0.1969
98.8
0.2038
102.3
0.2105
35 6.2710.01049
6.080
14.90
96.1
0.0328
0.1968
99.6
0.2037
103.1
0.2103
40
7.03 0.01053
5.460
16.00
96.8
0.0349
0.1968
100.3
0.2036
103.8
0.2101
45
7.88
0.01057
4.920
17,00
97.6
0.0370
0.1967
101.1
0.2035
104.6
0.2099
50
8.79
0.01062
4.440
18.10
98.4
0.0391
0.1967
101.9
0.2034
105.4
0.2098
55
9.80
0.01066
4.020
19.10
99.2
0.0412
0.1967
102.7
0.2033
106.2
0.2097
60
10.90
0.01071
3.640
20.20
100.0
0.0432
0.1967
103.5
0.2033
107.0
0.2096
65
12.10
0.01076
3.300
21.30
100.8
0.0453
0.1967
104.3
0.2032
107.8
0.2094
70
13.40
0.01081
3.000
22.40
101.5
0.0473
0.1967
105.0
0.2032
108.5
0.2093
75
14.80
0.01086
2.740
23.50
102.2
0.0493
0.1967
105.7
0.2031
109.2
0.2092
80
16.30
0.01091
2.500
24.50
102.9
0.0513
0.1966
106.4
0.2030
109.9
0.2090
85
17.90
0.01096
2.280
25.60
103.6
0.0533
0.1966
107.1
0.2029
110.6
0.2089
90
19.70
0.01101
2.090
26.70
104.4
0.0553
0.1966
107.9
0.2028
111.4
0.2088
95
21.60
0.01106
1.918
27.80
105.1
0.0573
0.1966
108.6
0.2028
112.1
0.2087
100
23.60
0.01111
1.761
28.90
105.7
0.0593
0.1965
109.2
0.2027
112.7
0.2085
105
25.90
0.01116
1.620
30.10
106.4
0.0613
0.1965
109.9
0.2026
113.4
0.2084
As an example in the interpretation of the chart consider the case when
moist air at a temperature of 80 F and a partial vapor pressure of 0.5 in
of mercury flows through a bed of silica gel which is at a temperature of
80 F. The chart indicates that the equilibrium of pressure between the
air-vapor mixture and the bed is reached when the dry bed has adsorbed
moisture to the extent of 31 per cent of the weight when dry. When this
happens the bed can adsorb no more moisture unless its temperature
is changed.
In practice however the adsorbent bed is seldom held at a steady tem-
perature in air conditioning applications and neither is the adsorption
process permitted to continue until moisture equilibrium is reached
Instead, the^bed temperature varies and the bed is re-activated before
equilibrium is approached. While charts of this kind can show the
limiting properties of the substances they are seldom directly applicable
to the solution of air conditioning problems unless considerable additional
information is available. This takes the form of performance data cover-
ing the characteristics of the equipment in which the adsorbent bed is
placed. Such performance data are beyond the scope of this chapter.
Liquid Absorbents
Any absorbent substance may be used as an air drying agent if it has a
JS^wCTSf loW*Vhan. the 7aP°r P«^re in the i-vapor mixture
from which the moisture is to be removed. Absorbents are character-
istically water solutions of materials in which the vapor pressure is
44
CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS
reduced to a suitable level by governing the concentration of the solution.
In addition to haying a suitable low vapor pressure, a practical absorbent
must also be widely available at economical cost, be non-corrosive,
odorless, non-toxic, chemically inert against any impurities in the air
stream, stable over the range of use and especially it must not precipitate
out at the lowest temperature to which the apparatus is exposed. It must
have low viscosity and be capable of being economically regenerated or
concentrated after having been diluted by absorbing moisture.
Water solutions, or brines, of the chlorides of various inorganic elements
such as calcium chloride and lithium chloride are the absorbents most
frequently used in connection with air conditioning applications and de-
tailed attention is confined to these two in this chapter.
Nature of Absorption Process
The application consists of bringing the air-vapor stream into intimate
contact with the absorbent, permissably by passing the air stream through
a finely divided spray of the brine but more generally by passing the air
over a metal surface coil where the liquid absorbent presents a large
surface to the air stream. The difference in vapor pressures causes some
of the vapor in the air-vapor mixture to migrate into the brine. Here it
condenses into liquid water and decreases the concentration of the absor-
bent. In order that the process be continuous means must be provided
for counteracting the diluting effect of the extracted moisture and also for
maintaining the temperature of the brine sufficiently low to hold the
desired vapor pressure.
As the water vapor is added to the absorbent and condenses, it gives up
its latent heat of condensation which tends to raise the temperature of
both the absorbent and the moist air stream. For every pound of water
absorbed and condensed the heat added to the air stream and the brine
TABLE 6. PROPERTIES OF WATER
SAT.
TEMP.
F
ABS
PRESS.
LB PER
3d IN.
VOLUME
HEAT CONTENT AND ENTROPY TAKEN FBOM -1-32 F
Heat Content
Entropy
50 F Superheat
100 F Superheat
Liquid
Vapor
Liquid
Vapor
Liquid
Vapor
HtCt.
Entropy
HtOL
Entropy
32
0.0887
0.01602
3296.0
0.00
1073.0
0.0000
2.1826
1096.9
2.2277
1120.8
2.2688
35
0.1000
0.01602
2941.0
3.02
1074.4
0.0062
2.1724
1098.3
2.2172
1122.2
2.2581
40
0.1217
0.01602
2441.0
8.05
1076.8
0.0163
2.1555
1100.6
2.2000
1124.5
2.2406
45
0.1475
0.01602
2034.0
13.07
1079.2
0.0262
2.1390
1102.9
2.1832
1126.7
2.2234
50
0.1780
0.01602
1702.0
18.08
1081.5
0.0361
2.1230
1105.2
2.1667
1129.0
2.2066
55
0.2140
0.01603
1430.0
23.08
1083.9
0.0459
2.1073
1107.5
2.1506
1131.3
2.1902
60
0.2561
0.01603
1206.0
28.08
1086.2
0.0556
2.0920
1109.8
2.1349
1133.5
2.1742
65
0.3054
0.01604
1021.0
33.08
1088.6
0.0652
2.0771
1112.2
2.1196
1135.8
2.1585
70
0.3628
0.01605
868.0
38.07
1090.9
0.0746
2.0625
1114.5
2.1046
1138.1
2.1432
75
0.4295
0.01606
740.0
43.06
1093.2
0.0840
2.0483
1116.7
2.0900
1140.3
2.1283
80
0.507
0.01607
632.9
48.05
1095.5
0.0933
2.0344
1119.0
2.0758
1142.5
2.1138
85
0.596
0.01609
543.3
53.04
1097.8
0.1025
2.0208
1121.2
2.0619
1144.7
2.0996
90
0.698
0.01610
467.9
58.03
1100.0
0.1116
2.0075
1123.4
2.0483
1146.8
2.0857
95
0.815
0.01612
404.2
63.01
1102.3
0.1206
1.9946
1125.6
2.0350
1148.9
2.0721
100
0.949
0.01613
350.3
68.00
1104.6
0.1296
1.9819
1127.9
2.0220
1151.1
2.0588
105
1.101
0.01615
304.4
72.98
1106.8
0.1384
1.9695
1130.2
2.0093
1153.2
2.0458
For properties of steam at high temperatures, see Page 28.
45
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 7. DEW-POINT OF AIR IN EQUILIBRIUM WITH LITHIUM CHLORIDE SOLUTIONS
CONCENTRATION* IN GRAM MOLS OF LITHIUM CHLORIDE PER 1000 GRAINS WATER
o.o 2.0 , 4.0 6.0
5.0
10.0
12.0 14.0 16.0 , 18.0 ! 20.0 ! 22.0 j 24.0 ! 26.0 J 28.0 , 30.0
320315.2308,7
299.9
290.2
279.7
269.4
259.6251.5244.1236.5,230.0223.8218.6214.5210.3
300295.4289.1
280.5
270.9
260.6
250.5
240.8232.6225.4218.0211.8i205.8200.8196.9,192.8
280;275.6269.5261.1
251.7
241.5
231.6
222.2 214.0206.7,199.7 193.5187.8 183.2179.3)175.2
260255.8250.0241.9
232.6
222.7
212.8
203.5 195.5188.4 181.7:175.41170.0 165.6'162.0 158.4
240236.0230.4222.5
213.5
203.8
194.2
185.0177.1 170.0,163.6157.5'152.21148.3 144.6140.5
220216.2210.8203.2
194.4
184.9
175.5
166.4 158.6 151 .6 145.3139.6 134.6,130.7 127.3124.2
200196.41191-2
183.9
175.4
166.1
156.7
148.0 140.3 133.5,127.3;121.9!117.0113.3 110.1
180 176.6;171.6 164.7
146.4
147.3
138.1
129.6 122.1;115.5 109.4 104.2| 99.6 96.0, i
160:156.8,152.1
;i45.4
137.4
128.6
119.7
111.3103.9, 97.4 91.61 86.61 82.21
140137.0132.6
126.1
118.4
109.9
101.3
93.1
85.9, 79.5 73.8| 69.0' ;
120J117.2 113.0 106.8
99.4
91.1
82.7
74.71 67.8; 61.5! 56.0: ' ; [
110107.3il03.2l 97.2
89.9
81.9
73.5
65.6: 58.8 52.6| 47.1| • !
100
97.4
93.4
87.5
80.5
72.7
64,4
56.6: 49.8 43.7i 38.2! !
90
87.5
83.6
77.9
71.0
63.3
54.2,
47.61 40.8 34.8;' 29.3' • '
|
80
77.6
73.8
68.4
61.6
54.0
46.1
38.5: 31.8! 25,9: 20.6
i
70 67.7
64.0
58.7
52.2
44.8
37.0
29.5
22.91 17.2, 12.0
60| 57.8
54.3
49.1
42.7
35.5
27.9
20.5
14.0; 83
'
40
38.0
34.7
29.9
23.9
16.9
9.6
2.4'-3.9! i
20
15.1
10.7
5.0
-1.7;
-8.7
-15.4! ; 1 : ; ' j
0
-4.5
-8.6
-13.9
-20.2
-27.0
-33.3
|!l;!
;
1 1 1
1
combined is obtainable from steam tables. For instance, at 60 F the
amount of this heat is about 1057 Btu. In addition to this heat there is
involved also the so-called heat of mixing which is frequently considerable.
Temperature-Pressure-Concentration Relations
Since the absorption process can continue only as long as there is a
difference in vapor pressure between the absorbent and the air-vapor
mixture and since at a given temperature of the absorbent the vapor
pressure depends on the concentration of the solution, evidently there
TABLE 8. DENSITY OF LITHIUM CHLORIDE SOLUTIONS
CONCENTRATION
MoLSLiCJPKB
1000 GRAINS
WATER
TEMPERATURE DEQ F
0
50
100
150
200
250
300
0
2
1.045
1.037
1.026
1.012
4
1.090
1.085
1.076
1.064
1.052
6
1.124
1.119
1.111
1.100
1.087
8
1.156
1.150
1.143
1.132
1.122
10
1,188
1.181
1.172
1.162
1.152
1.142
12
1,217
1.209
1.199
1.188
1.178
1.168
14
1.242
1.235
1.225
1.214
1.203
1.192
16
1.257
1.248
1.236
1.226
1.215
18
1.279
1.270
1.259
1.248
1.237
20
1.291
1.280
1.279
1.568
22
1.310
1.289
1.278
1.267
24
1.317
1.307
1.296
1.286
26
1.313
1.312
1.302
28
1.338
1.327
1.318
30
1.34
1.33
32
1.35
46
CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS
TABLE 9. VISCOSITY OF LITHIUM CHLORIDE SOLUTIONS (MILLIPOISE)
TEMP.
DEGF
CONCENTRATION IN JM.OLAL
0
2
4
6
8
10
12
14
16
18
20
22
24
0
56.75
72.44
97.05
136.8
199.5
20
28.91
37.07
47.42
63.09
84.94
123.3
178.6
40
15.45
19.91
25.53
32.58
43.05
58.48
81.10
116.1
165.6
60
11.02
14.26
18.37
23.55
30.90
41.40
56.62
79.80
111.2
156.3
80
8.61
11.19
14.42
18.62
24.32
32.28
43.45
60.26
82.04
113.8
100
6.82
8.89
11.48
14.94
19.36
25.59
33.96
46.13
61.52
84.72
118.3
120
5.60
7.31
9.51
12.30
15.92
20.99
27.67
36.64
48.31
65.77
89.95
140
4.70
6.15
8.07
10.42
13.43
17.66
22.96
30.06
38.99
52.48
71.12
95.94
160
4.01
5.25
6.92
8.93
11.51
15.00
19.36
25.06
32.14
42.76
56.89
75.86
106.2
180
3.48
4.56
6.01
7.78
10.00
12.91
16.56
21.28
27.10
35.48
46.45
60.67
84.33
200
3.05
4.01
5.28
6.86
8.79
11.22
14.32
18.28
23.12
29.92
38.55
50.70
67.92
220
2.72
3.58
4.72
6.14
7.83
9.93
12.59
16.00
20.14
25.64
32.96
43.05
56.49
240
2.43
3.21
4.25
5.50
7.02
8.83
11.12
14.09
17.62
22.18
28.31
36.98
47.42
260
2.19
2.90
3.84
4.94
6.46
7.91
9.91
12.47
15.50
19.36
24.60
31.92
40.55
280
2.00
2.66
3.52
4.51
5.75
7.19
8.97
11.27
14.00
17.22
21.78
28.05
35.56
300
1.86
2.48
3.28
4.17
5.32
6.67
8.28
10.38
12.82
15.70
19.68
25.12
31.92
320
1.74
2.32
3.08
3.89
4.94
6.19
7.73
9.64
11.86
14.45
18.03
22.80
29.11
must be a relation between these quantities which if known would state
the limits of the process. The relationship would also depend on the
absorbent being used, and would have to be determined for each substance
used as an absorbent. Fig. 2 shows this relationship graphically for
lithium chloride. It will be noted that this chart is essentially similar
to that shown in Fig. 1 and its direct usefulness is limited by much the
same considerations.
In order to permit numerical calculations of air conditioning problems
it is desirable to have tables for use instead of a chart like Fig. 2, and
Tables 7, 8, 9 and 10 can be used in making calculations for lithium
chloride.
TABLE 10. PROPERTIES OF LITHIUM CHLORIDE SOLUTIONS
CONCENTRATION
MOLS (42.4 GRAMS
LiCZ PER 1000
GRAINS WATER)
PARTIAL HEAT
OP MIXING AT
0 F BTU PER LB
TEMPERATURE COUP.
OP PARTIAL HEAT
OP MIXING BTTJ PER
LB PER F
SPECIFIC
HEAT AT
70 F
BOILING POINT
F
(AT 760 MM
EG)
FREEZING
POINT
SUBSTANCE THAT
FIRST SEPARATES
Our ON
FREEZING
0
0.0
0.0
0.998
212.0
32
Ice
2
2.04
-0.014
0.901
215.8
16.3
Ice
4
7.24
-0.036
0.831
221.5
-5.8
Ice
6
16.7
-0.069
0.778
228.9
-34.2
Ice
8
31.9
-0.109
0.739
238.1
-69
Ice
10
51.1
-0.143
0.710
248.4
-90
Ice
12
75.7
-0.160
0.687
258.8
-40
IAC13H&
14
90.8
-0.167
0.666
268.9
1
LiCl-3HiO
16
124.8
-0.176
0.647
277.9
36.5
LiCl-2H,0
18
145
-0.186
0.631
285.8
58.1
LiCl-2HzO
20
162
-0.194
0.617
293.2
86.4
LiCl-HzO
22
171
-0.20
0.604
300.2
133
LiCl-HzO
24
177
-0.20
0.59
307
156
UCl-HiO
26
182
-0.21
0.58
313
180
LiCLHlO
28
191
-0.21
0.575
318
190
LiCl-HzO
30
194
-0.21
0.57
323
195
UClr-H£>
32
198
-0.22
0.56
328
280
LiCl .
47
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Instead of tabulating the vapor pressure of the solution of lithium
chloride it ?s SefaSSto tabulate the dew-point of air m equilibrium
Sth lithium Sloridc, since it is easy to interpolate between values of
the dew ££t and not so easy to interpolate accurately between values of
apo pSre The valuesfor dew-point may be converted to vapor
CONCENTRATION, PER CENT
30 40 50
1000
500-
M1XTURE5 OF
SOLUTION AND LiCI-H2O
MIXTURES OF SOLUTION AND
LiCl -2H20
MIXTURES OF SOLUTION AND
LiCI-3H20
0.1
FIG.
10 15 20 25
CONCENTRATION, MOLAL
2. TEMPERATURE — PRESSURE — CONCENTRATIONS FOR LITHIUM CHLORIDE
pressures, relative humidity, and wet-bulb of air in equilibrium by means
of the usual psychrometric chart or formula.
In Tables 7, 8, 9 and 10 the unit of concentration is the mol A 'M'
molal solution is denned as a solution containing M X 42.37 grains of
anhydrous lithium chloride per 1000 grains of water. The formula con-
necting concentration in mols with weight in per cent is equivalent to:
[100 X M X 42.37] -r [1000 + (M X 42.37)].
48
CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS
PROBLEMS IN PRACTICE
1 • What is the heat content above — 40 F of 2.5 Ib of ammonia when under a
pressure of 92.9 Ih per square inch gage and a temperature of 160 F?
First determine the condition of the ammonia at the stated temperature and pressure.
Do this by finding the absolute pressure which in this case is 92.9 Ib gage plus 14.7 or
107.6 Ib per square inch absolute. From Table 1 note that the saturation temperature
at this pressure is 60 F. Therefore, the ammonia is superheated 100 F, and the total heat
per pound can be read directly from the Table as 689.9 Btu. In the 2.5 Ib of ammonia
there are 2.5 X 689.9, or 1724.75 Btu.
2 • "What volume is necessary to accommodate 0.27 Ib of saturated Fi2 vapor
when compressed to 99.6 Ib gage?
The absolute pressure is 99.6 plus 14.7 or 114.3 Ib. In Table 3 find that one pound of
Fi2 vapor saturated occupies 0.368 cu ft. Then the 0.27 Ib would occupy 0.27 X 0.368,
or 0.099 cu ft.
3 • How much heat would be removed from air passing over a coil through
which 2 Ib of methyl chloride per minute is forced? The coil is under a gage
pressure of 64 Ib per square inch and the liquid refrigerant is completely vapor-
ized in passing through the coil.
Find that the absolute pressure is 64 plus 14.7 or 78.7 Ib per sq in. From Table 4 note
that the saturation temperature at this pressure is 75 F (nearly) and that the heat
content per pound of the vapor is 207.8 Btu. Also that the heat content of the liquid is
42.2 Btu per pound. Subtract 42.2 from 207.8 and 165.6 Btu per pound is the heat
necessary to change the liquid refrigerant to a vapor (latent heat). As the heat to
accomplish this change comes from the air around the coil, the heat removed from the
air is 165.6 Btu per pound of methyl chloride evaporated in the coil. When the refriger-
ant is circulated at 2 Ib per minute, 2 X 165.6, or 331.2 Btu per minute are removed from
the air, or refrigerating effect is produced at the rate of 331.2 -5- 200, or 1.65 tons.
4 • Calculate the dew-point, wet-bulb, relative humidity and absolute hu-
midity of air in equilibrium at 100 F with pure lithium chloride solution of
density 1.270.
From Table 8 the concentration of a solution of density 1.270 at 100 F is 18.0 M. From
Table 7 the dew-point of 18 M lithium chloride at 100 F is 43.7 F. From Table 6,
Chapter 1, the partial pressure of water over the solution is 0.2858 in. of Hg, the absolute
humidity is 42.00 grains per pound dry air, and the wet-bulb is 65.8 F. The relative
humidity is 14.0 per cent.
5 • Calculate the boiling point, and freezing point of 18 M lithium chloride
solutions.
From Table 10, boiling point (standard) is 285.8 F, freezing point is 58.1 F. The salt
precipitated on cooling to this temperature has the composition LiCl-2H20.
6 • Calculate the heat of vaporization of 1 Ib of water from a large amount of
lithium chloride solution at the boiling point.
The heat of boiling is equal to the heat of mixing plus the heat of boiling pure water at
the same temperature. The heat of mixing from Table 10 at 18 M and 285.8 F is (145
— 0.186 X 285.8) = 92 Btu per pound. The heat of vaporization of water from steam
tables at 285.8 F is 920 Btu per pound. Therefore the heat of vaporization of water
from the solution is 920 -f 92 = 1012 Btu per pound.
7 • One thousand pounds of air per minute at 100 F dry -bulb with a dew-point
of 70 F and a relative humidity of 39 per cent is passed over 18 M lithium chloride
solution. The rate of flow of the solution is 200 gpm and the entering tempera-
ture is 80 F. The air leaves the absorber at 85 F dry-bulb and dew-point of
35 F. Calculate (a) the heat to be removed from the lithium chloride solution
49
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
to maintain these conditions, and (6) the temperature rise of the solution in
passing through the absorber.
a. The heat content of the entering air: From Table 6, Chapter 1, weight of vapor at
70 F dew-point is 0.01574 ib times heat content of steam at 100 F dry-bulb is 1104.2
(Table 8, Chapter 1) equals 17.41 Btu per pound plus heat content of dry air at 100 F
is 24.0 (Table 6, Chapter 1) resulting in heat content of mixture as 41.41 Btu per pound.
Similarly, the heat content of the leaving air: Weight of vapor at 35 F dew-point is
0.004262 X 1097.5 « 4.68 Btu per pound plus heat content of dry air at 85 F is 20.39
resulting in heat content of mixture as 25.07 Btu per pound.
Heat to be extracted from air is 1000 X (41.41 - 25.07) = 16,340 Btu per minute.
Add to this the heat of mixing of 18M lithium chloride at 80 F equals 145 - (0.186 X
80) = 130 Btu per pound (Table 10) or for 1000 Ib of air X (0,01574 - 0.00426) X 130 =
1494 Btu per minute. Heat to be removed from solution is 16,340 + 1494 = 17,834
Btu per minute.
6. The weight of solution circulated is 200 X 1.275 (Table 8) X 8.33 = 2124 Ib per
minute. Its heat capacity is 2124 X 0.631 (Table 10) = 1340 Btu per minute per degree
Fahrenheit. The temperature rise is 17,834 •*• 1340 = 13.31 F.
Chapter 3
PHYSICAL AND PHYSIOLOGICAL PRINCIPLES
OF AIR CONDITIONING
Vitiation of Air, Heat Regulation in Man, Effects of Heat,
Effects of Cold and Temperature Changes, Acclimatization,
Effective Temperature Index of Warmth, Optimum Air Condi-
tions, Winter and Summer Comfort Zone, Optimum Humid-
ity, Air Quality and Quantity, Air Movement and Distribution,
Natural and Mechanical Ventilation, Heat and Moisture
Losses, Ultra- Violet Radiation and lonization, Recirculation
and Ozone, Ventilation Standards
VENTILATION is defined in part as " the process of supplying or
removing air by natural or mechanical means to or from any space."
(See Chapter 45,) The word in itself implies quantity but not necessarily
quality. ^ From the standpoint of comfort and health, however, the
problem is now considered to be one of securing air of the proper quality
rather than of supplying a given quantity.
The term air conditioning in its broadest sense implies control of any or
all of the physical or chemical qualities of the air. More particularly, it
includes the simultaneous control of temperature, humidity, movement,
and purity of the air. The term is broad enough to embrace whatever
other additional factors may be found desirable for maintaining the
atmosphere^of occupied spaces at a condition best suited to the physio-
logical requirements of the human body.
VITIATION OF AIR
Under the artificial conditions of indoor life, the air undergoes certain
physical and chemical changes which are brought about by the occupants
themselves. The oxygen content is somewhat reduced, and the carbon
dioxide slightly increased by the respiratory processes. Organic matter,
which is usually perceived as odors, comes from the nose, mouth, skin
and clothing. The temperature of the air is increased by the metabolic
processes, and the humidity raised by the moisture emitted from the skin
and lungs. There is also a marked decrease in both positive and negative
ions in the air of occupied rooms but the significance of this factor is
still questionable1.
Contrary to old theories, the usual changes in oxygen and carbon
dioxide are of no physiological concern because they are much too small
even under the worst conditions. The amount of carbon dioxide in air is
Changes in Ionic Content in Occupied Rooms Ventilated, by Natural and MechanicalTMethods by
C. P. Yaglou, L. C. Benjamin and S. P. Choate (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 191).
51
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
often used in ventilation work as an index of odors of human origin, but
the information it affords rarely justifies the labor involved in making the
observation2- 3. Little is known of the identity and physiological effects of
the organic matter given off in the process of respiration. The former
belief that the discomfort experienced in confined spaces was due to some
toxic volatile matter in the expired air is now limited, in the light of
numerous researches, to the much less dogmatic view that the presence of
such a substance has not been demonstrated. The only certain fact is
that expired and transpired air is odorous and offensive, and it is capable
of producing loss of appetite and a disinclination for physical activity.
These reasons, whether esthetic or physiological, call for the introduction
of a certain minimum amount of clean outdoor air to dilute the odoriferous
matter to a concentration which is not objectionable.
A certain part of the dissemination of disease in confined spaces is
caused by the emission of pathogenic bacteria from infected persons.
Droplets sprayed into the air in talking, coughing, sneezing, etc., do not
all fall immediately to the ground within a few feet from the source, as it
was formerly believed. The large droplets do, of course, but minute
droplets less than 0.1 mm. in diameter evaporate to dryness before the}'
fall the height of a man. Nuclear residues from such sources, which may
contain infective organisms drift long distances with the air currents and
the virus may remain alive long enough to be transmitted to other persons
in the same room or building. Wells4 recovered droplet nuclei from
cultures of resistant micro-organisms a week after inoculation into a
tight chamber of 300 cu ft capacity. Typical organisms of infections of
the upper respiratory tract (pneumococcus type I, B. diphtheriae, Strep-
tococcus hemolyticus, and Streptococcus viridans) were found to die
out quite soon when exposed to light and air, and could be recovered from
the air in small numbers only 48 hours after inoculation/ Organisms
typical of the intestinal tract (B. coli, B. typhosus, B. paratyphosus,
A. and B. dysenteriae) were not recovered 12 hours after inoculation.
The significant factors in infection are believed to be the numbers, of
infective organisms encountered, the frequency of exposure, and the
resistance of the individual including the degree of acquired immunity.
The probability of encountering a sufficient number of organisms to
break down the natural body defense is related to the air space per person
and the quantity of clean air supplied. Except in badly ventilated rooms,
the danger is believed to be "much contracted in space, limited in time
and restricted to comparatively few diseases."5
^ Practical possibilities in sterilizing air supplies by the use of ultra-
violet light are now being studied6.
The primary factors in air conditioning work, in the absence of any
specific contaminating source, are temperature, radiation, drafts and
TRAJ?sSo^AVolC1^9nS19Sd AiJ6?{8triblltion' by R C Houghten and J. L. Blackshaw (A.S.H.V.E.
v inleontiiQ7An RW\rements, *>y c- p- Yaglou, E. C. Riley and D. I. Coggins (A.S.H.V.E. TRANSACTIONS,
vol. <U, laoO, p. L63).
oi^"*001* Infection and Sanitary Air Control, by W. F. Wells, (Journal Industrial Hygiene, November,
oOj.
B^TcSiVN1l?Ui9&fnd Hygiene' by Muton J- Rosenau (6th edition, pp. 909-917, D. Appleton-
slTsa^^gO)2' ^OU Exp°Sed t0 UttxBrVtolet Radiation in Air. by W. F. Wells, and G. M. Fair (Science,
52
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
body odors. As compared with these physical factors, the chemical
factors are, as a general rule, of secondary importance.
HEAT REGULATION IN MAN
The importance of the thermal factors arises from the profound in-
fluence which they exert upon body temperature, comfort and health.
Body temperature depends on the balance between heat production and
heat loss. The heat resulting from the combustion of food within the
body maintains the body temperature well above that of the surrounding
air. At the same time, heat is constantly lost from the body by radiation,
conduction and evaporation. Since, under ordinary conditions, the body
temperature is maintained at its normal level of about 98.6 F, the heat
production must be balanced by the heat loss. In healthy persons this
takes place automatically by the action of the heat regulating mechanism.
According to the general view, special areas in the skin are sensitive to
heat and cold. Nerve courses carry the sense impressions to the brain and
the response comes back over another set of nerves, the motor nerves, to
the musculature and to all the active tissues in the body, including the
endocrine glands. In this way, a two-sided mechanism controls the body
temperature by (1) regulation of internal heat production (chemical
regulation) , and (2) regulation of heat loss by means of automatic varia-
tion in the rate of cutaneous circulation and the operation of the sweat
glands (physical regulation). The mechanisms of adjustment are complex
and little understood at the present time. Coordination of these dif-
ferent mechanisms seems to vary greatly with different air conditions.
With rising air temperatures up to 75 F or 80 F, metabolism, or internal
heat production, decreases slightly7, probably by an inhibitory action on
heat producing organs, especially the adrenal glands, which seem to exert
the major influence on basic combustion processes in the body. The blood
capillaries in the skin become dilated by reflex action of the vasomotor
nerves, allowing more blood to flow into the skin, and thus increase its
temperature and consequently its heat loss. The increase in peripheral
circulation is at the expense of the internal organs. If this method of
cooling is not in itself sufficient, the stimulus is extended to the sweat
glands which allow water to pass through the surface of the skin, where it
is evaporated. This method of cooling is the most effective of all, as long
as the humidity of the air is sufficiently low to allow for evaporation. In
high humidities, where the difference between the dew-point temperature
of the air and body temperature is not sufficient to allow rapid evapora-
tion, equally good results may be obtained by increasing the air move-
ment, and hence the heat loss by conduction and evaporation.
In cold environments, in order to keep the body warm there is an actual
increase in metabolism brought about partly by voluntary muscular con-
tractions (shivering) and partly by an involuntary reflex upon the heat
producing organs. The surface blood vessels become constricted, and
the blood supply to the skin is curtailed by vasomotor shifts to the internal
organs in order to conserve body heat. The sweat glands become inactive.
7Heat and Moisture Losses from the Human Body and Their Relation to Air Conditioning Problems,
by F. C. Houghten, W. W. Teague, W. E. Miller and W. P. Yant (A.S.H.V.E. TRANSACTIONS, Vol. 35,
1929, p. 245).
53
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
EFFECTS OF HEAT
Although the human organism is capable of adapting itself to variations
in environmental conditions, its ability to maintain heat equilibrium is
limited. The upper limit of effective temperature to which the human
organism is capable of adapting itself without serious discomfort or
injury to health is 90 deg ET for men at rest and between 80 and 90 deg
ET for men at work depending upon the rate of work. Within these
limits a new equilibrium is established at a higher body temperature level
through a chain of physiological adjustments. The heat regulating center
fails, when the external temperature is so abnormally high that bodily
heat cannot be eliminated as fast as it is produced. Part of it is retained
in the body, causing a rise in skin and deep tissue temperature, an increase
in the heart rate, and accelerated respiration. (See Table 1.) In extreme
TABLE 1. PHYSIOLOGICAL RESPONSES TO HEAT OF MEN AT REST AND AT WORK*
MEN AT WOBK
ACTUAL
MEN AT RBST
90,000 FT-LB of WORK PER HOUE
EfTccxtni
TBJCP.
TEMP.
IDio
FAHR)
Rise in
Rectal
Temp.
Fahrper
Hour)
Increase
in Pulse
Rate
(gate per
Min per
Hour)
Loss in Body
Weight by
Perspiration
(Lb perHr)
Total Work
Accomplished
(Ft-Lb)
Rise in
Body Temp.
(Deg Fair
per Hr)
Increase in
Pulse Rate
(Beat* per
Min per Hr)
Approximate
Loss in Body
Wt. by Per-
spiration (Lb
per Hr)
60
225,000
0.0
6
0.5
70
o.o
6
6.2~
225,000
0.1
7
0.6
80
96.1
0.0
0
0.3
209,000
0.3
11
0.8
85
96.6
0.1
i
0.4
190,000
0.6
17
1.1
90
97.0
0.3
4
0.5
153,000
1.2
31
1.5
95
97.6
0.9
15
0.9
102,000
2.3
61
2.0
100
99.6
2.2
40
1.7
67,000
4.0
103b
2.7
105
104.7
4.0
83
2.7
49,000
6.0*>
158b
3.5*>
110
5.9b
137b
4.0*>
37,000
8.5b
237*
4.4b
•Data by A.S.H.V.E. Research Laboratory.
bCompnted va!ue from exposures lasting less than one hour.
heat, the metabolic rate is markedly increased owing to the excessive rise
in body temperature8, and a vicious cycle results which may eventually
lead to serious physiologic damage.
Examples of this are met with in unusually hot summer weather and in
hot industries where the radiant heat from hot objects renders heat loss
from the body by radiation and convection impossible. Consequently,
the workers depend entirely on evaporation for the elimination of body
heat. They stream with perspiration and drink liquids abundantly to
replace the loss.
One of the deleterious effects of high temperatures is that the blood is
diverted from the internal organs to the surface capillaries, in order to
serve in the process of cooling. This affects the stomach, heart, lungs and
other vital organs, and it is suggested that the feeling of lassitude and
discomfort experienced is due in part to the anaemic condition of the brain
The stomach loses some of its power to act upon the food, owing to a
54
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
diminished secretion of gastric juice, and there is a corresponding loss in
the antiseptic and antifermentive action which favors the growth of
bacteria in the intestinal tract9. These are considered to be the potent
factors in the increased susceptibility to gastro-intestinal disorders in hot
summer weather. The victim may lose appetite and suffer from indiges-
tion, headache and general enervation, which may eventually lead to a
premature old age.
In warm atmospheres, particularly during physical work, a considerable
amount of chloride is lost from the system through sweating. The loss of
this substance may lead to attacks of cramps, unless the salts are replaced
in the drinking water. In order to relieve both cramps and fatigue,
Moss10 recommends the addition of 6 grams of sodium chloride and 4 grams
of potassium chloride to a gallon of water.
The deleterious physiologic effects of high temperatures exert a power-
ful influence upon physical activity, accidents, sickness and mortality.
Both laboratory and field data show clearly that physical work in warm
atmospheres is a great effort, and that production falls progressively as
the temperature rises. The incidence of industrial accidents reaches a
minimum at about 68 F, increasing above and below that temperature.
Sickness and mortality rates increase progressively as the temperature
rises.
EFFECTS OF COLD AND TEMPERATURE CHANGES
The action of cold on human beings is not well known. Cold affects the
human organism in two ways: (1) through its action on the body as a
whole, and (2) through its action on the mucous membranes of the upper
respiratory tract. Little exact information is available on the latter.
On exposure to coldr the loss of heat is increased considerably and only
within certain limits is compensation possible by increased heat produc-
tion and decreased peripheral circulation. The rectal temperature often
rises upon exposure to cold but the pulse rate and skin temperature fall.
The blood pressure increases, owing to constriction in the peripheral
vessels. Just how cold affects health is not well understood. It imposes
an extra load upon the heat-producing organs to maintain body tempera-
ture. The strain falls largely upon digestion, metabolism, blood circu-
lation, and the kidneys, and indirectly upon the nervous system11.
Although the seasonal increase in morbidity and mortality sets in with
the approach of cold weather and subsides in the warm summer months,
little is known of the specific causative factors and their mechanism of
action. Over-crowding of buildings, overheated rooms, lack of venti-
lation, and close personal contacts are frequently held responsible for our
winter ills, but the evidence is not conclusive.
In extremely cold atmospheres compensation by increased metabolism
becomes inadequate. The body temperature falls and the reflex irritability
of the spinal cord is markedly affected. The organism may finally pass
into an unconscious state which ends in death.
•innueucc of Effective Temperature upon Bactericidal Action of Gastro-intestinal Tract, by Arnold and
Brody (Proceedings Society Exp. Biol. Mcd. Vol. 24, 1927, p. 832).
10Some Effects of High Air Temperatures upon the Miner, by K. N. Moss (.Transactions Institute of
Mining Engineers, Vol. 66, 1924, p. 284).
"Loc. Cit. Note 5.
55
HEATING VENTIIATING AIR CONDITIONING GUIDE 1938
Cannon showed that excessive loss of heat is associated with increased
activity of the adrenal medulla12. The extra output of adrenin hastens
heat production which protects the organism against cooling. Bast13
found a degeneration of thyroid and adrenal glands upon exposure to cold.
A moderate amount of variability in temperature is known to be
beneficial to health, comfort, and the performance of physical and mental
work. On the other hand, extreme changes in temperature, such as those
experienced in passing from a warm room to the cold air out-of-doors,
appear to be harmful to the tissues of the nose and throat which are the
portals for the entry of respiratory diseases.
Experiments show that chilling causes a constriction of the blood
vessels of the palate, tonsils, throat, and nasal mucosa, which is accom-
panied by a fall in the temperature of the tissues. On re-warming, the
palate and throat do not always regain their normal temperature and
blood supply. This anaemic condition favors bacterial activity and it
probably plays a part in the disposition of common cold and other
respiratory diseases. It is believed that the lowered resistance is due to a
diminution in the number and phagocytic activity of the leucocytes
(white blood cells) brought about by exposure to cold and by changes
in temperature.
Sickness records in industries seem to strengthen this belief. The
Industrial Fatigue Research Board of En'gland14 found that in workers
exposed to high temperatures and to changes in temperature, namely,
steel melters, puddlers, and general laborers, there is an excess of all
sickness, the excess among the puddlers being due chiefly to respiratory
diseases and rheumatism. The causative factor was not the heat itself
but the sudden changes in temperature to which the workers were exposed.
The tin-plate millmen who were not exposed to chills, since they work
almost continuously throughout the shift, had no excess of rheumatism
and respiratory diseases. On the other hand, the blast-furnacemen, who
work mostly in the open, showed more respiratory sickness than the steel
workers. This experience in British factories is well in accord with the
findings in American industries15- 16. According to these data the highest
pneumonia death rate is associated with dust, extreme heat, exposure to
cold, and to sudden changes in temperature.
ACCLIMATIZATION
Acclimatization and the factor of psychology are two important in-
fluences in air conditioning which cannot be ignored. The first is man's
ability to adapt himself to changes in air conditions; the second is an
intangible matter of habit and suggestion.
Some persons regard the unnecessary endurance of cold as a virtue.
^ f. Cannon, A. Guerido, S. W. Britten
- Bast* j- s- Supernaw' B- Lieberman and j- Munr°
Lolhdeon)°n ^ Sted Industry' by H' M' Vernon industrial Fatigue Research
telWfarf Bulletin,
Bloomfield<
56
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
They believe that the human organism can adapt itself to a wide range of
air conditions with no apparent discomfort or injury to health. In the
light of the present knowledge of air conditioning these views are not
justified. Acclimatization to extreme conditions involves a strain upon
the heat regulating system and it interferes with the normal physiologic
functions of the human body. Thousands of years in the heat of Africa
do not seem to have acclimatized the Negro to a temperature averaging
80 F. The same holds true of northern races with respect to cold, although
the effects are mitigated by artificial control. All this seems to indicate
that adaptation to an environment averaging between 60 and 80 F is a
very primitive trait17.
Within these limits, however, there does occur a definite adaptation to
external temperature level. People and animals raised under conditions
of tropical moist heat have a lower rate of heat production than do those
who grow up in cooler environments. This causes them to stand chilling
poorly as they are unable to quickly increase internal combustion to keep
up the body temperature. For this reason they have trouble standing
the cold, stormy weather of the temperate zones, and when exposed to it
are very susceptible to respiratory infections. Likewise, people living in
cool climates suffer greatly in the moist heat of the tropics until their
adrenal activity has slowed down. Within a couple of years, however,
they find themselves standing the heat much better and disliking cold.
They become acclimated by a definite change in the combustion level
within the body18.
In certain individuals the psychologic factor is more powerful than
acclimatization. A fresh air fiend may suffer in a room with windows
closed regardless of the quality of the air. As a matter of fact, instances
are known in which paid subjects refused to stay in a windowless but
properly conditioned experimental chamber because the atmosphere felt
suffocating to them upon entering the room.
EFFECTIVE TEMPERATURE INDEX OF WARMTH
Sensations of warmth or cold depend, not only on the temperature of
the surrounding air as registered by a dry-bulb thermometer, but also
upon the temperature indicated by a wet-bulb thermometer. Dry air at
a relatively high temperature may feel cooler than air of considerably
lower temperature with a high moisture content. Air motion makes any
moderate condition feel cooler.
On the other hand, in cold environments an increase in humidity
produces a cooler sensation. The dividing line at which humidity has no
effect upon warmth varies with the air velocity and is about 46 F (dry-
bulb) for still air and about 51, 56 and 59 F for air velocities of 100, 300
and 500 fpm, respectively. Radiation from cold or warm surfaces is
another important factor under certain conditions.
Combinations of temperature, humidity and air movement which
induce the same feeling of warmth are called thermo-equivalent con-
"Civilization and Climate, by Ellsworth Huntington, Yale University Press, 1924.
"Air Conditioning in its Relation to Human Welfare, by C. A. Mills (A.S.H.V.E. TRANSACTIONS, Vol.
40, 1934, p. 289).
57
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
I jj
-50
FIG. 1. EFFECTIVE TEMPERATURE CHART SHOWING NORMAL SCALE OF EFFECTIVE
TEMPERATURE. APPLICABLE TO INHABITANTS OF THE UNITED STATES UNDER
FOLLOWING CONDITIONS:
i/*** c.ustomary indoor clothing. B. Activity: Sedentary or light muscular work. C. Heating
Methods: Convection type. i.e. warm air, direct steam or hot water radiators, plenum systems. amnn*
58
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
ditions. A series of tests19- 20» «• 22 at the A.S.H.V.E. Research Labora-
tory, Pittsburgh, established the equivalent conditions met with in
general air conditioning work. This scale of thermo-equivalent conditions
not only indicates the sensation of warmth, but also determines the
physiological effects on the body induced by heat or cold. For this reason,
it is called the effective temperature scale or index.
Effective temperature is an empirically determined index of the degree
of warmth perceived^ on exposure to different combinations of tempera-
ture, humidity, and air movement. It was determined by trained subjects
who compared the relative warmth of various air conditions in two ad-
joining conditioned rooms by passing back and forth from one room to
the other.
Effective temperature is not in itself an index of comfort, except under
ordinary humidity conditions (30 to 60 per cent) when the individual is
least conscious of humidity. Moist air at a comparatively low tem-
perature, and dry air at a higher temperature may each feel as warm as
air of an intermediate temperature and humidity, but the comfort ex-
perienced in the three air conditions would be different, although the
effective temperature is the same.
Air of proper warmth may, for instance, contain excessive water vapor,
and in this way interfere with the normal physiologic loss of moisture
from the skin, leading to damp skin and clothing and producing more or
less discomfort; or the air may be excessively dry, producing appreciable
discomfort to the mucous membrane of the nose and to the skin which
dries up and becomes chapped from too rapid loss of moisture.
The numerical value of the effective temperature index for any given
air condition is fixed by the temperature of calm (15 to 25 fpm air move-
ment) and saturated air which induces a sensation of warmth or cold like
that of the given condition. Thus, any air condition has an effective
temperature of 60 deg, for instance, when it induces a sensation of warmth
like that experienced in calm air at 60 deg saturated with moisture. The
effective temperature index cannot be measured directly but it is com-
puted from the dry- and wet-bulb temperature and the velocity of air
using- charts (see Figs. 1 or 2, 3 and 4) or tables. The accuracy in esti-
mating effective temperature is ±0.5 F, because the human organism
cannot perceive smaller temperature differences. Therefore, there is no
justification in trying to read chart values closer than 0,5 F, as this
implies fictitious accuracy.
The charts shown in Figs. 1, 2, 3 and 4 apply to average normal^and
healthy persons adapted to American living and working conditions.
Application is limited to sedentary or light muscular activity, and to
rooms heated by the usual American convection methods (warm air,
central fan and direct hot water and steam heating systems) in which the
difference between the air and wall surface temperatures may not be too
"Determining Lines of Equal Comfort, by F. C. Houghten and C. P. Yaglou (A.S.H.V.E. TRANS-
ACTIONS, Vol. 29, 1923, p. 361).
'"Cooling Effect on Human Beings by Various Air Velocities, by F. C. Houghten and C. P. Yaglou
(A.S.H.V.E. TRANSACTIONS, Vol. 30, 1924, p. 193).
^Effective Temperature with Clothing, by C. P. Yaglou and W. E. Miller (A.S.H.V.E. TRANS-
ACTIONS, Vol. 31, 1925, p. 89).
^Effective Temperature for Persons Lightly Clothed and Working in Still Air, by F. C. Houghten, W. W.
Teague and W. E. Miller (A.S.H.V.E. TRANSACTIONS, Vol. 32, 1926, p. 315).
59
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
great. The charts do not apply to rooms heated by radiant method such
as British panel system, open coal fires and similar usages. They will
probably not apply to races other than the white or perhaps to inhabitants
of other countries where the living conditions, climate, heating methods,
and clothing are materially different than those of the subjects employed
in experiments at the Research Laboratory.
jo SNIIVMO
In rooms in which the average wall surface temperature is considerably
below or above air temperature, a correction must be applied to the
readings of the dry-bulb thermometer to allow for such negative or
positive radiation. In Fig. 5 is given the cooling effect of cold walls as
determined at the A.S.H.V.E. Research Laboratory" by trained subjects
l McDennott
60
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES or AIR CONDITIONING
passing back and forth from a small experimental room having three cold
walls, to a control room with walls and air at the same temperature.
It can be seen in Fig. 5 that with air and walls at 70 F in the control
(warm wall room), the cooling effect of three cold walls at 55 F of the
experimental room was 4 F. Therefore, for the same feeling of warmth,
3 S *
aiv AHQ jo amod *ad 3arusiow jo SNivyo
the temperature in the experimental room should be increased to 74 F.
The reverse would hold in rooms with high-wall surface temperature; a
lower air temperature would be required to compensate for positive
radiations to the occupants.
61
HEATING VENTIULTING AIR CONDITIONING GUIDE 1938
OPTIMUM Affi CONDITIONS
No single comfort standard can be laid down which would meet^ every
need. There is an inherent individual variation in the sensation of
warmth or comfort felt by persons when exposed to an identical atmos-
pheric condition. The state of health, age, sex, clothing, activity, and
AHQ JO QNnOd H3d 3Ur>JLSIOfl JO SNIVdO
the degree of acquired adaptation seem to be the important factors
affecting the comfort standards,
Since the prolonged effects of temperature, humidity and air move-
ment on health are not known to the same extent as their effects on com-
fort, the optimum conditions for health may not be identical with those
for comfort. On general physiologic grounds, however, the two do not
differ greatly since this is in accordance with the efficient operation of the
62
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
heat regulating mechanism of the body. This belief is strengthened by
results of studies on premature infants over a four-year period24. By
adjusting the temperature and humidity so as to stabilize the body tem-
perature of these infants, the incidence of diarrhoea and mortality was
decreased, gains in body weight increased and infections were reduced
to a minimum.
Winter Comfort Zone and Comfort Line
In Fig. 6 is shown the A.S.H.V.E. winter comfort zone which was
determined experimentally with large groups of men and women subjects
wearing customary indoor winter clothing. The extreme comfort zone
includes conditions between 60 and 74 deg ET in which one or more of the
experimental subjects were comfortable. The average comfort zone
WALL TEMPERATURE, DEG FAHR
FIG. 5. COOLING EFFECT OF THREE COLD WALLS IN A SMALL EXPERIMENTAL ROOM,
AS DETERMINED BY COMPARISON WITH SENSATIONS IN A ROOM OF UNIFORM
WALL AND AIR TEMPERATURE
includes conditions between 63 and 71 deg ET conducive to comfort in
50 per cent or more of the experimental subjects. The most popular
effective temperature was found to be 66 deg, and was adopted by the
Society25 as the winter comfort line for individuals at rest wearing custom-
ary winter clothing.
The comfort line separates the cool air conditions to its left from the
warm air conditions to its right. Under the air conditions existing along
or defined by the comfort line, the body is able to maintain thermal
"Application of Air Conditioning to Premature Nurseries in Hospitals, by C. P. Yaglou, Philip Drinker
and K. D. Blackfan (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 383).
»How to Use the Effective Temperature Index and Comfort Charts (A.S.H.V.E. TRANSACTIONS,
Vol. 38, 1932, p. 410).
63
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
90
, STILL AIR
' Air Mcveirent or Turbulence 15 to 25 ft. per min.
I ; A.S H.V.E. COMFORT CHART
(Cot>\ri£ht 1934}
Average Winter Comfort Zone —
'-— - Average Winter Comfort Line
K//V///I Average Summer Comfort Zone
— — — Average Summer Comfort Line
70 80 90 TOO
Pry Bulb Temperature F
FIG. 6. A.S.H.V.E. COMFORT CHART FOR AIR VELOCITIES OF 15 TO 25 FPM
(STILL AIR)*>, »
gfn^o^
8hSS. aPP y t0 "' department stores« ^d Belike whe?e the expo^elrie^^
equilibrium with its environment with the least conscious sensation to the
mdmdual, or with the minimum phsyiologic demand on the heat regulat-
ing mechanism. This environment involves not only the condition of the
air with respect to temperature and humidity, but also the condition of
the surrounding objects and wall surfaces. The comfort zone tests were
Zon^r^^^^^
CA.S.H.V.E.
64
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
made in rooms with wall surface temperatures approximately the same as
the room dry-bulb temperature. For walls of large area having unusually
high or low surface temperatures, however, a somewhat lower or higher
range of effective temperature is required to compensate for the increased
gain or loss of heat to or from the body by radiation as shown in Fig. 5
(See also Chapter 41).
The average winter comfort line (66 deg ET) applies to average
American men and women living inside the broad geographic belt across
the United States in which central heating of the convection type is
generally used during four to eight months of the year. It does not apply
to rooms heated by radiant energy, rooms with excessive glass area or
rooms with poorly insulated or cold walls. Even in the warm south and
southwestern climates, and in the very cold north-central climate of the
United States, ^the comfort chart would probably have to be modified
according to climate, living and working conditions, and the degree of
acquired adaptation.
In densely occupied spaces, such as classrooms, theaters and audi-
toriums, somewhat lower temperatures may be necessary than those
indicated by the comfort line on account of counter-radiation between the
bodies of occupants in close proximity28.
The sensation of comfort, insofar as the physical environment is con-
cerned, is not absolute but varies considerably among certain individuals.
Therefore, in applying the air conditions indicated by the comfort line,
it should not be expected that all the occupants of a room will feel per-
fectly comfortable. When the winter comfort line is applied in accordance
with the foregoing recommendations, the majority of the occupants will
be perfectly comfortable, but there will always be a few who would feel
a bit too cool and a few a bit too warm. These individual differences among
the minority should be counteracted by suitable clothing.
Air conditions lying outside the average comfort zone but within the
extreme comfort zone may be comfortable to certain persons. In other
words, it is possible for half of the occupants of a room to be comfortable
in air conditions outside the average comfort zone, but in the majority of
cases, if not in all, these conditions will be well within the extreme comfort
zone as determined experimentally.
The comfort chart (Fig. 6) applies to adults between 20 and 70 years
of age living in the northeastern parts of the United States. For pre-
maturely born infants, the optimum temperature varies from 100 F to
75 F, depending upon the stage of development. The optimum relative
humidity for these infants is placed at 65 per cent29. No data are yet
available on the optimum air conditions for full term infants and young
children up to school age. Satisfactory air conditions for these age
groups are assumed to vary from 75 F to 68 F with natural indoor humidi-
ties. For school children, the studies of the New York State Commission
on Ventilation place the optimum air conditions at 66 F to 68 F tempera-
ture with a moderate humidity (not specified) and a moderate but not
excessive amount of air movement (not specified)30.
»Loc. Cit. Note 27.
a»Loc. at. Note 24.
"Ventilation (Report N. Y. State Commission on Ventilation. E. P. Button and Co., N. Y., 1923).
65
HEATING VENTIIIATINO AIR CONDITIONING GUIDE 1938
Satisfactory comfort conditions for men at work are found to vary from
40 deg to 70 deg ET, depending upon the rate of work and amount of
clothing worn31. In hot industries, 80 deg ET is considered the upper
limit compatible with efficiency, and, whenever possible, this should be
reduced to 70 deg ET or less.
Summer Comfort Zones
The summer comfort zone is much more difficult to fix than the winter
zone owing to the complicating factor of sweating in warm weather. A
given air condition which is comfortable for persons with dry skin and
clothing may prove too cold for those perspiring, as is the case, for
instance, with employees and customers in a cooled store, restaurant, or
theater, on a warm summer day. The conditions to be maintained in
different types of public buildings depend to a large extent upon_ the oc-
cupants' length of stay and upon the prevailing outdoor condition.
In Fig. 6 is shown the summer comfort zone for exposures of 3 hours or
more, after adaptation has taken place. The average zone extends from
66 to 75 deg ET, with a comfort line at 71 deg ET, as determined at the
Harvard School of Public Health32. These effective temperatures average
about 4 deg higher than those found in winter when customary winter
clothing was worn. The variation from winter to summer is probably due
partly to adaptation to seasonal weather and partly to differences in the
clothing worn in the two seasons.
The best effective temperature (for exposures lasting 3 hours or more)
was found to follow the average monthly outdoor temperature more
closely than the prevailing outdoor temperature. It remained at approxi-
mately the same value in July, August and September, and although the
average monthly temperature did not vary much, the prevailing outdoor
temperature ranged from 70 F to 99.5 F. A decrease in the optimum
temperature became apparent only when the prevailing outdoor tempera-
ture fell to 66 F, which is below the customary room temperature in the
United States for summer and winter.
Crowding the experimental chamber lowered the comfortable effective
temperature from 70.8 deg when the gross floor area per occupant was
44 sq ft and the air space 380 cu ft, to 69.4 deg when the floor area was
reduced to 14 sq ft and the air space to 120 cu ft per occupant.
The basic summer comfort zone, shown in Fig. 6 has more academic
than practical significance. It prescribes conditions of choice for con-
tinuous exposures, as in homes, offices, etc., without regard to costs,
prevailing outdoor air conditions, and temperature contrasts upon
entering or leaving the cooled space. A great number of persons seem to
be content with a higher plane of indoor temperature, particularly when
the matter of first cost and cost of operation of the cooling plant is given
due consideration.
According to previous investigations33, an indoor temperature of about
80 F with relative humidities below 55 per cent, or 74.5 deg ET and lower,
result in satisfactory comfort conditions in the living quarters of a residence,
«Loc. Cit. Note 22.
»Loc. Cit. Note 27.
. . .
vf ^i?1? of Summer (Doling in the Research Residence for the Summer of 1934, by A. P. Kratz, S. Konzo,
M. K. Fahnestock and E. L. Broderick (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 207).
66
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES or AIR CONDITIONING
and while this condition is not representative of optimum comfort it
provides for sufficient relief in hot weather to be acceptable to the majority
of users. Experience in a number of air conditioned office buildings,
including the New Metropolitan Life Building in New York34, indicates
that a temperature of about 80 F with a relative humidity between 45 and
55 per cent (73 to 74.5 deg ET) is generally satisfactory in meeting the
requirements of the employees.
In artificially cooled theaters, restaurants, and other public buildings
where the period of occupancy is short, the contrast between outdoor and
indoor air conditions becomes the deciding factor in regard to the tem-
perature and humidity to be maintained. The object of cooling such
places in the summer is to provide sufficient relief from the heat without
causing sensations of chill or intense heat on entering and leaving the
building.
Effective temperatures as high as 75 F at times have been found satis-
factory in very warm weather. There are two schools of thought con-
cerning the relation between temperature and humidity to be maintained.
For a given effective temperature some engineers including the operators
of cooling plants favor a comparatively low temperature with a high
humidity as this results in a reduction of refrigeration requirements.
Preliminary experiments at the A.S.H.V.E. Laboratories35 would seem to
indicate no appreciable impairment of comfort with relative humidities
as high as 80 per cent, provided the effective temperature is between
70 and 75 deg,
The second school favors a higher dry-bulb temperature, according^ to
the prevailing outdoor dry-bulb, with a comparatively low humidity
(well below 50 per cent) ; the main purpose being to reduce temperature
contrasts upon entering and leaving the cooled, space and to keep the
clothing and skin dry. This second scheme requires more refrigeration
with the present conventional type of apparatus.
Current practice in theatres, restaurants, etc., follows a schedule
similar to that shown in Table 2, This schedule should be used^with con-
siderable judgment depending on the occupancy and local climatic
conditions. There are some indications that a definite indoor effective
temperature may be applicable throughout the cooling season, but
other observations seem to show that changing indoor conditions are
desirable with violently changing outdoor weather conditions. It is, in
fact, questionable whether entirely satisfactory air conditions could be
adduced for practical use to meet the changing requirements of patrons
from the time they enter to the time they leave a cooled space. Too
many uncontrollable variables enter into the problem. Work now going
on at the A.S.H.V.E. Laboratories and other interested institutions may
throw considerable light on this complex problem. _^
For cooled banks and stores where the customers come and go spending
»*The Air Conditioned System of the New Metropolitan Building— First Summer's Experience, by W. J.
McConnell and I. B. Kagey (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 217).
^Comfort Standards for Summer Air Conditioning, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E.
TRANSACTIONS, Vol. 42, 1936, p. 215). Cooling Requirements for Summer Air Conditioning, by F. C.
Houghten, F. E. Giesecke, Cyril Tasker and Carl Gutberlet (A.S.H.V.E. JOURNAL SECTION, Heating,
Piping and Air Conditioning, December, 1936, p. 681).
67
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2. DESIRABLE INSIDE CONDITIONS ix SUMMER CORRESPONDING
TO OUTSIDE TEMPERATURES**
Occupancy Over 40 Min
INSIDE AIR CONDITIONS
DEC F
Effective Dry-Bulb Wet-Bulb
Temperature Deg F , Deg F
Dew-Point
DegF
Relative Humid-
ity Per Cent
100
75 83
75 82
75 81
75 i 80
66
i 67
68
70
56
59
61
65
40
45
51
60
95
74
74
74
74
74
82
81
80
79
78
64
66
67
68
70
53
57
60
62
66
36
44
51
57
68
90
i
i
73
73
73
73
81
80
79
78
63
64
66
67
52
54
59
61
36
41
50
56
85 :
1
1
72
72
72
72
80
79
78
77
61
63
64
66
48
53
56
60
32
41
46
56
80
71
71
71
71
78
77
76
75
61
63
64
66
49
54
57
61
36
45
52
61
^Applicable to individuals engaged in sedentary or light muscular activity.
but a few minutes in the cooled space, observations36 indicate a schedule
about 1 deg dry-bulb or effective temperature higher than that shown in
Table 2. Laboratory experiments with exposures of 2 to 10 min indicate
temperatures 2 to 10 F higher than those in Table 2 but with much lower
relative humidities.
It should be kept in mind that southern people, with their more sluggish
heat production and lack of adaptability, will demand a comfort zone
several degrees higher than that for the more active people of northern
climates. Instead of the summer comfort line standing at 71 deg as here
given, it was found to be much higher for foreigners in Shanghai where
climatic conditions are similar to those of our gulf states. This difference
in adaptability of people forms a very real problem for air conditioning
engineers. Cooling of theaters, restaurants, and other public buildings in
southern climates cannot be based on northern standards without con-
siderable modification.
Optimum Humidity
Just what the optimum range of humidity is, is a matter of conjecture.
1 here seems to exist a general opinion, supported by some experimental
and statistical data, that warm, dry air is less pleasant than air of a
- bv J- H- Walker (Heating
68
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
moderate humidity, and that it dries up the mucous membranes in such
a way as to increase susceptibility to colds and other respiratory dis-
orders 37f 38> 39t Owing to the cooling effect of evaporation, higher tem-
peratures are necessary, and this condition may lead to discomfort and
lassitude. Moist air, on the other hand, interferes with the normal
evaporation of moisture from the skin, and again may cause a feeling of
oppression and lassitude, especially when the temperature is also high.
For the premature infant, a high relative humidity of about 65 per cent is
demonstrably beneficial to health and growth40 until the infants reach a
weight of about 5 Ib. No such clear-cut evidence exists in the case of
adult persons. In the comfort zone experiments of the A.S.H.V.E.
Research Laboratory, the relative humidity was varied between the
limits of 30 and 70 per cent approximately, but the most comfortable
range has not been determined. In similar experiments at the Harvard
School of Public Health, the majority of the subjects were unable to
detect sensations of humidity (i.e., too high, too low, or medium) when
the relative humidity was between 30 per cent and 60 per cent with
ordinary room temperatures. This is in accord with studies by Howell41,
Miura42 and others.
The limitation of the comfort zones in Fig. 6 with respect to humidity
must not be taken too seriously. Relative humidities below 30 per cent
may prove satisfactory from the standpoint of comfort, so long as ex-
tremely low humidities are avoided. From the standpoint of health,
however, the consensus seems to favor a relative humidity between 40 and
60 per cent. In mild weather such comparatively high relative humidi-
ties are entirely feasible, but in cold or sub-freezing weather they are
objectionable on account of condensation and frosting on the windows.
They may even cause serious damage to certain building materials of the
exposed walls by condensation and freezing of the moisture accumulating
inside these materials. Unless special precautions are taken to properly
insulate the affected surfaces, it will be necessary to reduce the degree of
artificial humidification in sub-freezing weather to less than 40 per cent,
according to the outdoor temperature. Information on the prevention of
condensation on building surfaces is given in Chapter 7. The principles
underlying humidity requirements and limitations are discussed more
fully elsewhere43.
The purpose of artificial humidification may be easily defeated by
failure to change the spray water of the humidifier at least daily. Where
this condition occurs, the air is characterized by a lack of freshness, and
under extreme conditions by a musty, sour odor in the conditioned space.
"Reactions of the Nasal Cavity and Post-Nasal Space to Chilling of the Body Surface, by Mudd, Stuart,
et al (Journal Experimental Medicine, 1921, Vol. 34, p. 11).
^Reactions of the Nasal Cavity and Post-Nasal Space to Chilling of the Body Surfaces, by A. Goldman,
et al and Concurrent Study of Bacteriology of Nose and Throat (Journal Infectious Diseases, 1921, Vol. 29,
p. 151).
S9The Etiology of Acute Inflammations of the Nose, Pharynx and Tonsils, by Mudd, Stuart, et al (Am.
Otol., Rhinol., and Laryngol., 1921).
«Loc. Cit. Note 24.
^Humidity and Comfort, by W. H. Howell (The Science Press, April, 1931).
^Effect of Variation in Relative Humidity upon Skin Temperature and Sense of Comfort, by U. Miura
(American Journal of Hygiene, Vol. 13, 1931, p. 432).
^Humidification for Residences, by A. P. Kratz, University of Illinois (Engineering Experiment Station
Bulletin No. 230, July 28, 1931).
69
HEATING VENTIIATING AIR CONDITIONING GUIDE 1938
Affi QUALITY AND QUANTITY
Air Quality
In occupied spaces in which the vitiation is entirely of human origin,
the chemical composition of the air, the dust, and often the bacteria con-
tent may be dismissed from consideration so that the problem consists in
maintaining a suitable temperature with a moderate humidity, and in
keeping the atmosphere free from objectionable odors. Such unpleasant
odors, human or otherwise, can be easily detected by persons entering the
room from clean, odorless air.
In industrial rooms where the primary consideration is the control of
air pollution (dusts, fumes, gases, etc.), or contamination not removable
at the source of production, the clean air supply must be sufficient to
dilute the polluting elements to a concentration below the physiological
threshold (see Chapters 4 and 26).
Air Quantity
The air supply to occupied spaces must always be adequate to satisfy
the physiological requirements of the occupants. It must be sufficient to
maintain the desired temperature, humidity, and purity with reasonable
uniformity and without drafts. In many practical instances there are
two air quantities to be considered, (a) outdoor air supply, and (b) total
air supply. The difference between the two gives the amount of air to be
recirculated.
When the only source of contamination is the occupant, the minimum
quantity of outdoor air needed appears to be that necessary to remove
objectionable body odors, or tobacco smoke. The concentration of body
odor in a room, in turn, depends upon a number of factors, including
socio-economic status of occupants, outdoor air supply, air space allowed
per person, odor adsorbing capacity of air conditioning processes, tem-
perature, and other factors of secondary importance. With any given
group of occupants and type of air conditioner the intensity of body odor
perceived upon entering a room from relatively clean air was found to
vary inversely with the logarithm of outdoor air supply and the logarithm
of the air space allowed per person*
The minimum outdoor air supply necessary to remove objectionable
body odors under various conditions, as determined experimentally at the
Harvard School of Public Health44, is given in Table 3.
Outdoor air requirements for the removal of objectionable tobacco
smoke odors have yet to be determined. Practical values in the field vary
from 5 to 15 cfm per person; this air quantity may and should be a part
of that necessary for other requirements, i.e., removal of body odors, heat,
moisture, etc.
The total quantity of air to be circulated through an enclosure is
governed largely^ by the needs for controlling temperature and air dis-
tribution when either heating or cooling is required. The factors which
determine total air quantity include the type and nature of the building,
locality, climate, height of rooms, floor area, window area, extent of
occupancy, and last but not least, the method of distribution.
Serious difficulties are often encountered in attempting to cool a room
**Loc. Cit Note 3.
70
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
with a poor distribution system or with an air supply which is too small to
result in uniform distribution without drafts. Some systems of distribu-
tion produce drafts with but a few degrees temperature rise, while other
systems operate successfully with a temperature rise as high as 35 F.
The total air quantity introduced in any particular case is inversely pro-
portional to the temperature rise, and depends largely upon the judgment
and ingenuity of the engineer in designing the most suitable system for the
particular conditions.
TABLE 3. MINIMUM OUTDOOR AIR REQUIREMENTS TO REMOVE OBJECTIONABLE
BODY ODORS
(Provisional values subject to revision upon completion of work)
TYPE OP OCCUPANTS
AIR SPACE PER
PEBSON Cu FT
OUTDOOR* AIR SUPPLY
CFM ?BR PERSON
Heating season with or without recirculation. Air not conditioned.
Sedentary adults of average socio-economic status
Sedentary adults of average socio-economic status
100
200
25
16
Sedentary adults of average socio-economic status —
Sedentary adults of average socio-economic status.
300
500
12
7
Laborers
200
23
Grade school children of average class
100
29
Grade school children of average class
Grade school children of average class
200
300
21
17
Grade school children of average class
500
11
Grade school children of poor class
200
38
Grade school children of better class
200
18
Grade school children of best class
100
22
Heating season. Air humidified by means of centrifugal humidifier. Water
atomization rate 8 to 10 gph. Total air circulation SO cfm per person.
Sedentary Adults
200
12
Summer season. Air cooled and dehumidified by means of a spray dehumidifier.
Spray water changed daily. Total air circulation 80 cfm per person.
Sedentary Adults
200
<4
a Impressions upon entering room from relatively clean air at threshold odor intensity.
The changes in moisture content resulting from occupation in the
atmosphere of a room supplied with various volumes of outside air is
shown in Fig. 7. Data are given for an adult, 5 ft 8 in. in height, weighing
150 Ib and having a body surface of 19.5 sq ft and for a child, 12 years of
age, 4 ft 7 in. in height weighing 76.6 Ib and having a body surface area
of 12.6 sq ft. Also given in Fig. 7 is the temperature of incoming air
necessary to maintain a room temperature of either 70 or 80 F as indicated
assuming that there is no heat gain or loss to the room by transmission
through the walls, solar radiation or other sources.
71
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
AIR MOVEMENT AND DISTRIBUTION
Stagnant warm air, no matter how pure, is not stimulating and it
detracts to some extent from the quality of air. Experience, and recent
field studies by the A.S.H.V.E. Research Laboratory45 place the desirable
air movement between 15 and 25 fpm under ordinary room temperatures
during the heating season. Objectionable drafts are likely to occur when
the velocity of the air current is 40 fpm and the temperature of the air
current 2 F or more below the customary winter room temperature.
Higher velocities are not objectionable in the summer time when the air
i — i — i
ADULTS IN 80 F AIR
!>CHILDREN IN 80 F AIR
.ADULTS IN 70 F AIR
(^.CHILDREN IN 70 F AIR
CHILDREN IN 80 F AIR
ULTS IN 80 F AIR
CHILDREN IN 70 F AIR
ADULTS IN 70 F AIR
12 16 20 24 28-
RATE OF AIR SUPPLY
CUBIC FEET PER MINUTE PER OCCUPANT
FIG. 7. RELATION AMONG RATE OF AIR CHANGE PER OCCUPANT, MOISTURE CONTENT
OF ENCLOSURE, AND DRY-BULB TEMPERATURE OF INCOMING AIR
temperature exceeds 80 F. Variations in air movement and temperature
in different parts of occupied rooms are often indicative of relative air
distribution. The work of the A.S.H.V.E. Research Laboratory indicates
that an air movement between 15 and 25 fpm with a temperature variation
of 3 F or less in different parts of a room, 36 in. above floor, insure satis-
factory distribution. Considerable evidence was obtained in these tests
to show that measurements of carbon dioxide are not essential for the
study of air distribution, or for indirect measurements of outdoor air
^Classroom Drafts in Relation to Entering Air Stream Temperature, by F. C. Houghten,
Cart Gutberlet and M. F. Lichtenfels (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 268).
, H. H. Trimble,
72
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES or AIR CONDITIONING
TABLE 4. RELATION BETWEEN METABOLIC RATE AND ACTIVITY*
ACTIVITY
HOTJRLT META-
BOLIC RATE FOB
AYG. PERSON OB
TOTAL HEAT
DISSIPATED,
BTU PER HOUR
HOURLT
SENSIBLE
HEAT
DISSIPATED,
BTU PER
HOUR
HOURLY
LATENT
HEAT
DISSIPATED,
BTU PER
HOUR
MOISTURE DISSIPATED,
PER HOUR
GRAINS
LB
Average Person Seated at Rest1..
Average Person Standing at Rest1
384
431
225
225
159
206
1070
1390
0.153
0.199
Tailor2
482
225
257
1740
0.248
Office Worker Moderately Active
490
225
265
1790
0.256
Clerk, Moderately Active,
Standing at Counter.—
600
225
375
2530
0.362
Book Binder2.
626
225
401
2710
0.387
Shoe Maker2; Clerk, Very Active
Standing at Counter
661
225
436
2940
0.420
Pool Player
680
230
450
3040
0.434
Walking^ mph3. 4; Light
Dancing
761
250
511
3450
0.493
Metalworker2
862
277
585
3950
0.564
Painter of Furniture2.
876
280
596
4020
0.575
Restaurant Serving, Very Busy..
1000
325
675
4560
0.651
Walking 3 mph8
1050
346
704
4750
0.679
Walking 4 mph8. *; Active
Dancing, Roller Skating.
1390
452
938
6330
0.904
Stone Mason2
1490
490
1000
6750
0.964
Bowling
1500
490
1010
6820
0.974
Man Sawing Wood2.
1800
590
1210
8170
1.167
Slow Run4
2290
Walking 5 mph8
2330
Vgry Severe Exercise**
2560
Maximum Exertion Different
People4.
3000 to 4800
aMetabolism rates noted based on tests actually determined from the following authoritative sources:
iA.S.H.V.E. Research Laboratory; *Becker and Hamalainen; 'Douglas, Haldane, Henderson and Schneider;
^Henderson and Haggard; and "^Benedict and Carpenter. Metabolic rates for other activities estimated.
Total heat dissipation integrated into latent and sensible rates by actual tests for metabolic rates up to
1250 Btu per hour, and extrapolated above this rate. Values for total heat dissipation apply for all atmos-
pheric conditions in a temperature range from approximately 60 to 90 F dry-bulb. Division of total heat
dissipation rates into sensible and latent heat holds only for conditions having a dry-bulb temperature of
79 F. For lower temperatures, sensible heat dissipation increases and latent heat decreases, while for
higher temperatures the reverse is true.
TABLE 5.
DEGREES OF PERSPIRATION FOR PERSONS SEATED AT REST UNDER
VARIOUS ATMOSPHERIC CONDITIONS
DEGREE OF PERSPIRATION*
ATMOSPHERIC CONDITION
95 Per Cent Relative
Humidity
20 Per Cent Relative
Humidity
E.T.
D.B.
W.B.
E.T.
D.B.
W.B.
Forehead clammy ..
73.0
73.0
79.0
80.0
84.5
88.0
88.5
73.6
73.6
79.7
80.8
85.4
89.0
89.5
72.4
72.4
78.4
79.4
84.0
87.6
88.1
75.0
75.0
81.0
87.0
86.5
94.0
90.0
87.0
87.0
97.5
109.4
108.5
125.2
116.0
60.7
60.7
67.5
75.2
74.6
85.4
79.5
Body clammy.. . .
Body damp . .— — -
Beads on forehead
Body wet.
Perspiration on forehead runs and drips
Perspiration runs down body- .
•Forty per cent of subjects registered degree of perspiration equal to or greater than indicated.
73
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
! 1 ' '
-H~~*"
JTU-
*— U
1 ! ' | ' M ~
' I ' ! ' • ' i
, ' ' • ' ^
—^ ;• "'-•y^i-
p-r- : , i i I n I , J |
.1 «;':,•';!' — i i > L
1 ' ' ' ' ^
• : JT ''^
! i • ' i >^r i M$
' l^^^i :
ni;b/ffl li
wm
&L-"---
:^::::fe
"Ib
— ' —
, 1
-^-H-
— 1 ' '
"t~h~
L-in
jf
r4-
T^
^
d
^c
-r
4
s
ft
jT
s f
' I : / /
1 'A A
£H4#
!/ / j
/ j
I/I ' 1 1 1
ijr^i.y- * \
/.SiA'fo i -r^
lJTT!1f MM
/ ' i /[ * ' ' — i
7 — y- -HI — H-I —
M j , 1 , . | 1
TTrmTr
b
- ;^
::"::__ b
44-
1 III
1 j J
i-LJL
1
Y
1
-
^M 4-
p>
I 11
.
fefe g«« *3sfs
§ ^g| 3 .|I|g
8" w o d ^sf Sc
?2,S ^fel^^a
8 8 § 8 §
o«oio-^<ON-
ClJt>s"S5D NVW 39VU3AV «0d 'BH H3d Til* "VIOL
05 B
oooooo
oooooo
— o»cor*<o
OJT35SBD NVW 39VH3AV tJO
oo
oo
evi —
U3d TO IB TV1QI
74
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
TABLE 6. DEGREES OF PERSPIRATION FOR PERSONS AT WORK UNT»ER VARIOUS
ATMOSPHERIC CONDITIONS
Work Rate 83,000 Ft Lb per Hour
DEGREE OF PERSPIRATION"
95 Per Cent Relative
Humidity
20 Per Cent Relative
Humidity
E. T.
D.B.
W.B.
•E. T.
D.B.
W.B
Forehead clammy
59.0
50.0
60.0
68.0
69.0
78.5
79.0
59.4
50.2
60.3
68.5
69.6
79.3
79.8
58.3
49.3
59.3
67.5
68.5
78.0
78.5
69.5
57.0
62.5
76.0
71.0
82.0
81.0
80.5
61.6
69.6
91.0
82.8
100.5
99.8
56.5
44.2
49.5
63.4
53.0
70.2
69.0
Body clammy
Body damp . .
Beads on forehead.
Body w^t
Perspiration on forehead runs and drips
Perspiration runs down body
ATMOSPHERIC CONDITION
aForty per cent of subjects registered degree of perspiration equal to or greater than indicated.
supply, which can be obtained more conveniently from the increase in
moisture content of the ventilating current.
HEAT AND MOISTURE GIVEN UP BY HUMAN BODY
In conditioning air for comfort and health it is necessary to know the
rate of sensible and latent heat liberation, from the human body, which in
conjunction with other heat loads (see Chapters 5 and 7) determine the
capacity of the conditioner. The data in common use are those of the
A.S.H.V.E. Research Laboratory46 shown in Figs. 8, 9, 10 and 11. Other
useful data are given in Tables 4, 5 and 6, which are self-explanatory.
ULTRA-VIOLET RADIATION AND IONIZATION
In spite of the rapid advances in the field of air conditioning during the
past few years, the secret of reproducing indoor atmospheres of as
stimulating qualities as those existing outdoors under ideal weather con-
ditions, has not as yet been found. Extensive studies have failed to
elucidate the cause of the stimulating quality of country air, qualities
which are lost when such air is brought indoors and particularly when it
is handled by mechanical means. Ultra-violet light and ionizatlon have
been suggested but the evidence so far is inconclusive or negative47.
*6Thermal Exchanges between the Bodies of Men Working and the Atmospheric Environment, by F. C.
Houghten, W. W. Teague, W. E. Miller and W. P. Yant (American Journal of Hygiene, Vol. XIII, No. 2.
March, 1931, pp. 415-431).
47Changes in Ionic Content in Occupied Rooms, Ventilated by Natural and Mechanical Methods, by
C. P. Yaglou, L. C. Benjamin and S. P. Choate (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 191). Physio-
logic Changes During Exposure to Ionized Air, by C. P. Yaglou, A. D. Brandt and L. C. Benjamin (A.S.
H.V.E. TRANSACTIONS, Vol. 39, 1933, p. 357). Diurnal and Seasonal Variations in the Small Ion Content
of Outdoor and Indoor Air, by C. P. Yaglou and L. C. Benjamin (A.S.H.V.E. TRANSACTIONS, Vol. 40,
1934, p. 271). The Nature of Ions in Air and Their Possible Physiological Effects, by L/. B. Loeb (A.S.
H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 101). The Influence of Ionized Air upon Normal Subjects, by
L. P. Herrington (Journal Clinical Investigation, 14, January, 1935). The Effect of High Concentrations
of Light Negative Atmospheric Ions on the Growth and Activity of the Albino Rat, by L. P. Herrington
and Karl L. Smith (Journal Ind. Hygiene, 17, November, 1935). Subjective Reactions of Human Beines
to Certain Outdoor Atmospheric Conditions, by C.-E. A. Winslow and L. P. Herrington (A.S.H.V.E.
TRANSACTIONS, Vol. 42, 1936, p. 119).
75
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
^1000
"-i i"< — *— t' 'jx^T F
H
I , ! M ,' "
U.
gonn
, . y^; -, -
900
, L. I , I ' ,' | , ! ' , ! I
jf i i _;
— Ann
, . i/Lj
1 ; ' i ' / ' i
i . / ^ -5000
S *VA/>
1 ' j/1 f
/ ^ z
i i X '
o
• • rii , | /! : •
j ; . ; j>" _ _, ^ -
< 600
1 . 'i 1 • : i 1 !/| . | i
/My^ ^ -
fj y i X^^T -
50O
i ' ! J ' ' /
g
2 t
^~ yf _3000
cf 40°
-j-
! ' / / ''
y~" ;-"
1 I
--U.
--J-H
f~l~ .x T ~^~^^ ^
-r-
£ 300:
x
|
r r--E-2ooo
*• £
=**oo
L
L.-JL-L-f?-^
-g__X =
at
-h-
4L*£'i£*-l L.J.
i- E-iooo
<!>
DRY BULB TEMPELRATURE *FAHR. g
FIG. 10. LATENT HEAT AND MOISTURE Loss FROM THE HUMAN BODY BY EVAPORATION
IN RELATION TO DRY-BULB TEMPERATURE FOR STILL AIR CoNDiTioNSa
/- -A.TMen working 66,150 ft-Ib per hour. Curve B — Men working 33,075 ft-lb per hour. Curve
C— Men working 16,638 ft-lb per hour. Curve D— Men seated at rest. Curves A and C drawn from data
at a dry-bulb temperature of 81.3 F only and extrapolating the relation between Curves B and D which
were drawn from data at many temperatures.
45° 50° 55° 60° 65° 70° 75°
DRY BULB TEMPERATURE *FAHR.
£OSS *ROM rai5 HUMAN BODY BY EVAPORATION, RADIATION AND CON-
RELATION TO DRY-BULB TEMPERATURE FOR STILL AIR CONDITION^
76
CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING
NATURAL AND MECHANICAL VENTILATION
Under favorable conditions natural ventilation methods properly com-
bined with means for heating may be sufficient to provide for the fore-
going objectives in homes, uncrowded offices, small stores, etc.
In large offices, large school rooms, and in public and industrial build-
ings, natural ventilation is uncertain and makes heating difficult. The
chief disadvantage of natural methods is the lack of control ; they depend
largely on weather and upon the velocity and direction of the wind.
Rooms on the windward side of a building may be difficult to heat and
ventilate on account of drafts, while rooms on the leeward side may not
receive an adequate amount of air from out-of-doors. The partial vacuum
produced on the leeward side under the action of the wind may even
reverse the flow of air so that the leeward half of the building has to take
the drift of the air from the rooms of the windward half. Under such
conditions no outdoor air would enter through a leeward window opening,
but room air would pass out.
In warm weather natural methods of ventilation afford little or no
control of indoor temperature and humidity. Outdoor smoke, dust and
noise constitute other limitations of natural methods.
RECmCULATION AND OZONE
The amount of recirculated air may be varied to suit changes in weather
and seasonal requirements, so as to conserve heat in winter and refrig-
eration in summer, but the saving in operating cost should not be obtained
at the expense of air quality.
Ozone has been used for deodorizing recirculated air by oxidation or
masking. Under favorable conditions some success is possible but from
the practical standpoint it is difficult to regulate the ozone output so as to
just neutralize undesirable odors at all times during the occupancy of a
room. The difficulties appear to be mainly due to a wide variability in
the rate of ozone disappearance in different rooms, or in the same room at
different times, according to the characteristics of a room, the absolute
humidity, impurities in the air, number and type of occupants, and
probably other factors which require considerable study before ozone can
be safely and economically applied.
The allowable concentrations in the breathing zone are very small,
between 0.01 to 0.05 parts of 03 per million parts of air. These are much
too small to influence bacteria. Higher concentrations are associated
with a pungent unpleasant odor and considerable discomfort to the
occupants. One part per million causes respiratory discomfort in man,
headaches and depression, lowers the metabolism, and may even lead to
coma48.
Toilets, kitchens, and similar rooms, in buildings using recirculation,
should be ventilated separately by mechanical exhaust in order to prevent
objectionable odors from diffusing into other parts of the building.
**The British Medical Journal. Editorial. June 25, 1932, p. 1182. See also Loc. Cit. Note 5.
77
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
PROBLEMS IN PRACTICE
1 • What are the most comfortable air conditions?
Comfort standards are not absolute, but they are greatly affected by the physical con-
dition of the individual, and the climate, season, age, sex, clothing, and physical activity.
For the northeastern climate of the United States, the conditions which meet the require-
ments of the majority of people consist of temperatures between 68 and 72 F in winter
and between 70 and 85 F in summer, the latter depending largely upon the prevailing
outdoor temperature. The most desirable relative humidity range seems to be between
30 and 60 per cent.
2 • Are the optimum conditions for comfort identical with those for health?
There are no absolute criteria of the prolonged effects of various air conditions on health.
For the present it can be only inferred that bodily discomfort may be an indication of
adverse conditions leading to poor health.
3 • Given dry-bulh and wet-bulb temperatures of 76 F and 62 F, respectively,
and an air velocity of 100 fpm, determine: (l) effective temperature of the
condition; (2) effective temperature with calm air; (3) cooling produced hy the
movement of the air.
(1) In Fig. 1 draw line AB through given dry- and wet-bulb temperatures. Its inter-
section with the 100 ft velocity curve gives 69 deg for the effective temperature of the
condition. (2) Follow line AB to the right to its intersection with the 20 fpm velocity
line, and read 70.4 deg for the effective temperature for this velocity or so-called still air.
(3) The cooling produced by the movement of the air is 70.4 - 69 = 1.4 deg ET.
4 • Assume that the design of an air conditioning system for a theater is to he
based on an outdoor dry-bulb temperature of 95 F and a wet-bulb temperature
of 78 F with an indoor relative humidity of 50 per cent. According to Table 2,
the dry-bulb temperature in the auditorium should be 80 F. Estimate the
sensible and latent heat given up per person.
The sensible heat given up per person per hour may be obtained from Fig. 9. With an
abscissa value of 80 F, Curve D for men seated at rest gives a value (on the ordinate
scale) of 220 Btu per person per hour as the sensible heat loss. The latent heat given up
by a person seated at rest may be obtained from Fig. 10. With an abscissa value of 80 F, '
Curve D indicates a latent heat loss of 175 Btu per hour (left hand scale) or a moisture
loss of 1190 grains per hour (right hand scale).
5 • Neglecting the gain or loss of heat by transmission or infiltration through
walls, windows and doors, how many cubic feet of outside air, with dry- and
wet-bulb temperatures of 65 F and 59 F, respectively, (63.1 deg ET) must be
supplied per hour to an auditorium containing 1000 people in order that the
inside temperature shall not exceed 75 F dry-bulb and 65 F wet-bulb?
Figs. 9 and 10 give 265 Btu sensible heat and 905 grains of moisture per person with a
dry-bulb temperature of 75 F in the auditorium. Therefore, 265,000 Btu of sensible
heat and 905,000 grains of moisture will be added to the air in the auditorium per hour.
Taking 0,24 as the specific heat of air, 2.4 Btu per pound of air will be absorbed in
raising the dry-bulb temperature from 65 to 75 F, and 265,000 -4- 2.4 - 110,400 Ib of
air or 110,400 X 13.4 = 1,479,000 cfh of air will be required. This is equivalent to
1,479,000 -5- (1000 X 60) = 24.7 cfm per person.
The ^moisture content of the inside air is 76 grains per pound of dry air and that of the
outside condition is 65 grains. From a psychrometric chart the increase in moisture
content will therefore be 11 grains per pound of dry air. Hence 905,000 + 11.0 = 82,300
Ib of air at the specified condition will be required. This is equivalent to 82,300 X 13 4
- 1,103,000 cfh of air or 1,103,000 -- (1000 X 60) - 18.4 cfm of air per person.
The higher volume of 24.7 cfm per person will be required to keep the dry-bulb tem-
perature from rising above the 75 F specified. The wet-bulb temperature will therefore
not rise to the maximum of 65 F.
78
Chapter 4
AIR POLLUTION
Classification of Air Impurities, Dust Concentrations, Air
Pollution and Health, Occlusion of Solar Radiation, Smoke
and Air Pollution Abatement, Dust and Cinders, Nature's
Dust Catcher
THE particulate impurities which contribute to atmospheric pollution
include carbon from the combustion of fuels, particles of earth, sand,
ash, rubber tires, leather, animal excretion, stone, wood, rust, paper,
threads of cotton, wool, and silks, bits of animal and vegetable matter,
and pollen. Microscopic examination of the impurities in city air shows
that a large percentage of the particles are carbon.
CLASSIFICATION OF AIR IMPURITIES
The most conspicuous sources of atmospheric pollution may be classi-
fied arbitrarily according to the size of the particles as dusts, fumes, and
smoke. Dusts consist of particles of solid matter varying from 1.0 to 150
microns in size, (micron = 0.001 millimeter or 1/25,000 in.) Fumes
t include particles resulting from chemical processing, combustion, explo-
sion, and distillation, ranging from 0.1 to 1.0 micron in size. The word
fumes may be applied also to mixtures of mists (liquid droplets) and gases
as acid mists. Smoke is composed of fine soot or carbon particles, usually
less than 0.1 micron in size, which result from incomplete combustion of
carbonaceous materials, such as. coal, oil, tar, and tobacco. In addition
to carbon and soot, smoke contains unconsumed hydrocarbon gases,
sulphur dioxide, carbon monoxide, and other industrial gases capable of
injuring property, vegetation, and health.
The lines of demarcation in these three classifications are neither sharp
nor positive, but the distinction is descriptive of the nature and origin of
of the particles, and their physical action. Dusts settle without appre-
ciable agglomeration, fumes tend to aggregate, smoke to diffuse. Particles
which approach the common bacteria in size — about 1 micron — are
difficult to remove from air and are apt to remain in suspension unless
they can be agglomerated by artificial means. The term fly-ash is usually
applied to the microscopic glassy spheres which form the principal solid
constituent of the effluent gases from powdered-coal fired furnaces.
Cinders denote the larger solid constituents which may be entrained by
furnace gases.
It is well established that particles larger than about 1 micron are
unlikely to remain suspended in air currents of moderate strength. Only
79
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
violent air motion will sustain them in air long enough for them to be
breathed. This means that, in hygenic problems, the engineer is con-
cerned mostly with suspensions of particles comparable to the common
D!AM.
OF
PAR-
TICLES
m
HICW113
SCALE OF
ATMOSPHERIC
IMPURITIES
RATE OF
SETTLING
IN F.PM.
FOR
SPHERED
OF
DENSITY I
AT 10* F.
NUMBER
OFPAR-
TICIESW
OMECUFT
SURFACE
AREA IN
SQUARE
INCHES
LAWS OF SETTLING
IN RELATION TO
PARTICLE SIZE
(LINES OF DEMARCATION APPRO*.)
AIR CONTAINING
.0006 GRAINS OF
IMPURITIES PER
CU.FT.(BEM31T<-0
8000
600O
p" :.. -i."..--. — r., -td
| PARTICLES SETTLE WITH CONSTANT VELOCITY |
PARTICLES FALL WITH
INCREASING VELOCITY
4000
£000
1000
800
600
400
200
100
SO
=^=^rz|:
790
.075
.000)65
C = 24.9VD«7
oVelocity ctn/s«c.
CWelocity ft/mm.
d«Diam of par-
ticle in cm.
D*Diam. of par-
ticlt in Microns
r« Radius of par-
ticle in cm.
g-SSlcm/aec*
acceleration
s,- Density of
particle
sz=Density of Air
(Very Small
relative to s,)
57* Viscosity of
air in poises
-!814xlO~Tfor
o.r at 70* F.
(Mean free
path of gas
molecules )
'•^^FP-
^H-J^^^
555
g
•00_0!3__
.003653
-
-1
-L." S)D <•
e*» ^,!ui O:
75
3
A|
•-f*i
i « ^
ff
iza ^
O u
— r-^r — *
STOKES
LAW
FOR AIR AT 70 *F.
c -300,460s,d*
C -.0059ZS.D*
CUNNINGHAM'S
60
40
20
10
8
3|
stgss
^
tf
532
600
75000
.0073
.0365 *
|&1N.SQ.
Is
JGp 3 ij
"
^-
5
si5" s i
t;
s
o*
1
^1<
1
G
Z
1
-|
m
148
JOT 5"
600.000
75X10*
.073
.365 3
3
tf
s!
H u*
CE
|
a.
:(
53 UJ o
S
a
.6
.4
.2
1
^^H
-K
_£j±jjU
002=1.4"
60XI07
8
.73
FACTOR
ifl
y
s
PCRHR.
MOtn-64
75x10*
3.65 »
f1"! «
ft S
2
<
C'-C OF STOKES IAW
K -.8 TO .86
uJ
UJ
s f
? k •
1
te.
ci
I
^
.01
PER HR.
i.e IN.SO.
PARTICLES N
GAS MOL
BROWN IAN
MOVEMENT
A=Vff 3^7
1OVE LIKE
&CULES
A- Distance of
motion m time t
R-Gas constant
-0.316x10''
T- Absolute
Temperature
N* Number of Gas
molecules in
onemoi-edOSxlO23
•fii
-^ —
Sti
ri—
— &
0
73XI011
UJ
— y:
0
en
t
5
-a*?
£s<
o5
; 5 «
hJ
a| 8 8
«»•
15- f
o
.OOI
0
60XI013
73.0
'-.5 8 j
— n
2
UZh
^.< w &
0
365 S
2.5350. FT.
f
-y
irl-y
-•
5
Compiled by W. G. Frank and Copyrighted.
FIG. 1. SIZES AND CHARACTERISTICS OF AIR-BORNE SOLIDS
bacteria in size. A notable exception to this size limitation is the common
hay-fever producing pollen such as that from rag-weed. Pollen grains
may be anything from fragments 15 microns in diameter to whole pollens
25 microns or more in size. Since the lower limit of visability to the
CHAPTER 4. AIR POLLUTION
TABLE 1. APPROXIMATE LIMITS OF INFLAMMABILITY OF SINGLE GASES AND VAPORS
IN AIR AT ORDINARY TEMPERATURES AND PRESSURES**
GAS OR VAPOR
LOWER LIMIT
VOLTJMB IN PER CENT
HIGHER LIMIT
VOLUME IN PER CENT
Hydrogen
4 1
74 o
Ammonia
16 0
27 0
Hydrogen sulphide
43
46 0
Carbon disulphide
1 0
50 0
Carbon monoxide
12 5
74 0
Methane
5 3
14 0
Methane (turbulent mixture)
5 0
15 0
Ethane
3 2
12 5
Propane-
2 4
9 5
Butane
19
85
Pentane
1 45
7 5
Ethylene
3 0
29 0
Acetylene -
3 0
Acetylene (turbulent mixture)
2 3
Benzene.
1 4
7 0
Toluene.
1 4
7 0
Cyclohexane
13
8 3
Methyl cyclohexane
1 2
Methyl alcohoL
7 0
Ethyl alcohol
4 0
19 0
Ethyl ether._ .. .
1 7
26 0
Benzine
1 1
Gasoline
1 4
6 0
Water gas
6 to 9
55 to 70
Ethylene oxide
3.0
80 0
Acetaldehyde
4 0
57 0
Furfural (125 C)
2.0
Acetone
3 0
11 0
Acetone (turbulent mixture)
2.5
Methyl ethyl ketone.
2 0
12 0
Methyl formate
6 0
20 0
Ethyl formate
3 5
16 5
Methyl acetate-
4 1
14 0
Ethyl acetate
2 5
11 5
Proovl acetate
2 0
Butyl acetate (30 C)
1.7
Ethyl nitrite.
3.0
Methyl chloride
8 0
19 0
Methyl bromide— ...
13.5
14 5
Ethyl chloride
4 0
15 0
Ethyl bromide
7 0
11 0
Ethylene dichloride
6 0
16 0
Dichlorethylene
10 0
13 0
Vinyl chloride,
4.0
22.0
Pyridine (70 C)
1.8
12 5
Natural gas
4 8
13 5
Illuminating gas
5.3
31 0
Blast-furnace eras
35 0
74 0
^Limits of Inflammability of Gases and Vapors, by H. F. Coward and G. W. Jones, (U. S. Bureau <
Mines, Bulletin No. 279, 1931).
81
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
average eye is around 50 microns all air floated material of this kind is too
small to identify without the aid of the microscope.
Mineral particles, such as grains of sand, bits of rock, volcanic ash, or
fly-ash, can be transported long distances under unusual circumstances.
Thus, the dust storms of 1935 in the Kansas district resulted in vast
amounts of fine top soil being thrown high into the air. Solar illumination
as far east as Boston was affected noticeably and particles as large as 40
to 50 microns were actually carried half way across the continent before
they settled out. In similar manner volcanic ash has been carried even
further. It is not surprising, therefore, that fly-ash from furnace gases,
cement dust and the like, can be carried for considerable distances and
occasionally the engineer is confronted with the problem of removing such
material before the air in question is suitable for use in building venti-
lation.
The physical properties of the particulate impurities of air are summar-
ized conveniently in the chart of Fig. 1.
In the case of gases the physical property which is probably of most
importance is inflammability. The best data available at present on this
subject are given in Table 1.
Dust Concentrations
It is customary to report dust concentrations as grains per 1000 cu ft
or milligrams per cubic meter. Gas concentrations are commonly' re-
corded as milligrams per cubic meter or as parts per million or as per
cent by volume. Typical ranges in dust concentrations as now found in
practical applications are given in Table 2.
TABLE 2. DCST CONCENTRATION RANGES IN PRACTICAL APPLICATIONS**
APPLICATION
GRAINS PER 1000 Cn FT
MGS PER Cu M
Rural and suburban districts
0 2 to 04
04. rn ft fc
Metropolitan districts
0 4 to 08
0 9 to 1 8
Industrial districts
0 8 to 15
1 8 to 3 5
Dusty factories or mines
4 0 to 80 0
10 to 200
Explosive concentrations (as of flour or soft coal)..
4000 to 8000
10,000 to 20,000
«1 grain per 1000 cu ft = 2.3 mgs per cubic meter; 1 oz per cubic foot =* 1 gram per liter.
The engineer frequently desires information regarding the effects of
various concentrations of gases or dusts upon man, as the success of a
particular installation may depend upon the maintenance of air which is
adequately clean. At the present time there are a number of organi-
zations working on this problem all of them publishing literature of
various kinds.1 References to books covering the hygienic significance,
determination and control of dust are listed at the end of this chapter.
m
meat of
f' S-P^lic Health Service; Division of Labor Standards, U. S. Depart-
of Toronto Medical School, Canada; Saranac Laboratories, Saranac Lake
' In", ^^S^A **- Harvard ^h001 of Public Health! BoS?, M£ .\
:1 '^ the Departraents of Health and °f Labor in the United States
82
CHAPTER 4. AIR POLLUTION
AIR POLLUTION AND HEALTH
The prevention of various diseases which result from exposure to
atmospheric impurities is an engineering problem. It is important for
the engineer to insure, by proper ventilation, suitable environments for
working or for general living. If the equipment used is to be successful, it
must operate automatically as in the modern air conditioned theatre or
railroad train.
In Table 3 are given data on permissable concentrations of various
substances, gases and dusts, which occur in industry. The prudent
TABLE 3. TOXICITY OF GASES AND FUMES IN PARTS PER 10,000 PARTS OF AiRa
VAPOR OB GAS
RAPIDLY
FATAL
MAXIMUM
CONCENTRATION
FOR FROM
M TO 1 HOUR
\
1 MAXIMUM
CONCENTRATION
FOR 1 HOUH
MAXIMUM
ALLOWABLE
FOR PROLONGED
EXPOSURE
Carbon monoxide
Carbon dioxide
40
800-1000
15-20
10
1
Hydrocyanic acid
30
\1A
'"y"
l.<
Ammonia
50-100
25
3
1
Hydrochloric acid gas
10-20
Ko
Chlorine....".
10
\s
Koo
Hydrofluoric acid gas._
2
Mo
3*33
Sulphur dioxide.-
4-5
M-l
s^.Q
Hydrogen sulphide
Carbon bisulphide.
10-30
5-7
11
2-3
5
1
\4
Phosphene
20
4-6
1 2
Arsine
2H
1A
Phosgene
Over 34
i/
Mnn
Nitrous furnes
2^-7i|
1-1 H
7Q
Benzene
190
31-47
lU-3
Toluene and xylene
190
31-47
Aniline
1-1^
Kn
Nitrobenzene
Hoo
i/
44 i\f\
Carbon tetrachloride
Chloroform
480
250
240
140
40
50
1
2
Tetrachlorethane _
Trichlorethylene
73
370
Ho
Methyl chloride.....
Methyl bromide
1500-3000
200-400
200-400
20-40
70
10
5-10
2
Lead dust.
0 15 mg/cu m
Quartz dust
1 mg/cu m
^Adapted from Y. Henderson and H. Haggard. (See ^oxtows Gases, 1927, and Lessotw Learned from
Industrial Gases and Fumes, Institute of Chemistry of Great Britain and Ireland, London, 1930.)
engineer will design equipment using these bench marks as the upper
limits of pollution. In general it is good practice to avoid recirculation
of air which contains originally toxic substances. Obviously there may be
exceptions to this rule, but it is one which is generally being followed in
current practice.
' Bronchitis is the chief condition associated with exposure to thick dust,
and follows upon inhalation of practically any kind of insoluble and non-
colloidal dust. Atmospheric dust in itself cannot be blamed for causing
tuberculosis, but it may aggravate the disease once it has started.2
'Physiological Response of the Peritoneal Tissue to Dusts Introduced as Foreign Bodies, by Miller
and Sayers (U. S. Public Health Reports, 49:80, 1934).
83
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
The sulphurous fumes and tarry matter in smoke are more dangerous
than the carbon. In foggy weather the accumulation of these substances
in the lower strata may be such as to cause irritation of the eyes, nose, and
respiratory passages, leading to asthmatic breathing and bronchitis and,
in extreme cases, to death. The Meuse Valley fog disaster will probably
become a classic example in the history of gaseous air pollution. Re-
leased in a rare combination of atmospheric calm and dense ^fog, it^is
believed that sulphur dioxide and other toxic gases from the industrial
region of the valley caused 63 sudden deaths, and injuries to several
hundred persons.
Carbon monoxide from automobiles and from chimney ^ gases consti-
tutes another important source of aerial pollution in busy cities. During
heavy traffic hours and under atmospheric conditions favorable to con-
centration, the air of congested streets is found to contain enough CO to
menace the health of those exposed over a period of several hours, par-
ticularly if their activities call for deep and rapid breathing.^ In open air
under ordinary conditions the concentration of CO in city air is insufficient
to affect the average city dweller or pedestrian.
Occlusion of Solar Radiation
The loss of light, particularly the occlusion of solar ultra-violet light
due to smoke and soot, is beginning to be recognized as a health problem
in many industrial cities. Measurements of solar radiation in Baltimore3
by actinic methods show that the ultra-violet light in the country was
50 per cent greater than in the city. In New York City4 a loss as great as
50 per cent in visible light was found by the photo-electric cell method.
Recent studies5 in Pittsburgh indicate that heavy smoke pollution is
definitely unhealthful. Heretofore adequate proofs on this point were
lacking.
The aesthetic and economic objections to air pollution are so definite,
and the effect of air-borne pollen can be shown so readily as the cause of
hay fever and other allergic diseases, that means and expenses of pre-
vention or elimination of this pollution are justified.
SMOKE AND AIR POLLUTION ABATEMENT
Successful abatement of atmospheric pollution requires the combined
efforts of the combustion engineer, the public health officer, and the
public itself. The complete electrification of industry and railroads, and
the separation of industrial and residential communities would aid
materially in the effective solution of the problem.
In the large cities where the nuisance from smoke, dust and cinders is
the most serious, limited areas obtain some relief by the use of district
heating. The boilers in these plants are of large size designed and oper-
ated to burn the fuel without smoke, and some of them are equipped with
dust catching devices. The gases of combustion are usually discharged at
'Effects of Atmospheric Pollution Upon Incidence of Solar Ultra-Violet Light, by J. H. Shrader, M. H.
Coblentz and F. A. Korff (American Journal of Public Health, p. 7, Vol. 19, 1929).
'Studies in Illumination, by J. E. Ives (U. S. Public Health Service Bulletin No. 197, 1930).
'Pneumoconiosis in the Pittsburgh district, Based on a Study of 2,500 Post Mortem Examinations
made in Pittsburgh Hospitals, by Schnurer et al (Journal Industrial Hygiene, 17:294, March, 1935).
84
CHAPTER 4. AIR POLLUTION
a much higher level than is possible in the case of buildings that operate
their own boiler plants.
In general, time, temperature and turbulence are the essential require-
ments for smokeless combustion. Anything that can be done to increase
any one of these factors will reduce the quantity of smoke discharged.
Especial care must be taken in hand-firing bituminous coals. (See
Chapter 9.)
Checker or alternate firing, in which the fuel is fired alternately on
separate parts of the grate > maintains a higher furnace temperature and
thereby decreases the amount of smoke.
Coking and firing, in which the fuel is first fired close to the firing door
and the coke pushed back into the furnace just before firing again, pro-
duces the same effect. The volatiles as they are distilled thus have to
pass over the hot fuel bed where they will be burned if they are mixed with
sufficient air and are not cooled too quickly by the heat-absorbing surfaces
of the boiler.
Steam or compressed air jetst admitted over the fire, create turbulence
in the furnace and bring the volatiles of the fuel more quickly into contact
with the air required for combustion. These jets are especially helpful
for the first few minutes after each firing. Frequent firings of small
charges shorten the smoking period and reduce the density. Thinner
fuel beds on the grate increase the effective combustion space in the
furnace, supply more air for combustion, and are sometimes effective in
reducing the smoke emitted, but care should be taken that holes are not
formed in the fire. A lower volatile coal or a higher gravity oil always
produces less smoke than a high volatile coal or low gravity oil used in
the same furnace and fired in the same manner.
The installation of more modern or better designed fuel burning equip-
ment, or a change in the construction of the furnace, will often reduce
smoke. The installation of a Dutch oven which will increase the furnace
volume and raise the furnace temperature often produces satisfactory-
results.
In the case of new installations, the problem of smoke abatement can
be solved by the selection of the proper fuel-burning equipment and
furnace design for the particular fuel to be burned and by the proper
operation of that equipment. Constant vigilance is necessary to make
certain that the equipment is properly operated. In old installations the
solution of the problem presents many difficulties, and a considerable
investment in special apparatus is necessary.
Legislative measures at the present time are largely concerned with the
smoke discharged from the chimneys of boiler plants. Practically all of
the ordinances limit the number of minutes in any one hour that smoke of
a specified density, as measured by comparison with a Ringelmann Chart
(Chapter 44), may be discharged.
These ordinances do not cover the smoke discharged at low levels by
automobiles, and, although they have been instrumental in reducing the
smoke emitted by boiler plants, they have, in many instances, increased
the output of chimney dust and cinders due to the use of more excess air
and to greater turbulence in the furnaces.
Legislative measures in general have not as yet covered the noxious
85
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
gases, such as sulphur dioxide and sulphuric acid mist, which are dis-
charged with the gases of combustion. ^ Where high sulphur coals are
burned, these sulphur gases present a serious problem.
DUST AND CINDERS
The impurities in the air other than smoke come from so many sources
that they are difficult to control. Only those which are produced in
large quantities at a comparatively few points, such as the dust, cinders
and fly-ash discharged to the atmosphere along with the gases of com-
bustion from burning solid fuel, can be readily controlled.
Dusts and cinders in flue gas may be caught by various devices on the
market, such as fabric filters, dust traps, settling chambers, centrifugal
separators, electrical precipitators, and gas scrubbers, described in
Chapter 26.
The cinder particles are usually larger in size than the dust particles;
they are gray or black in color, and are abrasive. Being of a larger size,
the range within which they may annoy is limited.
The dust particles are usually extremely fine; they are light gray or
yellow in color, and are not as abrasive as cinder particles. Being ex-
tremely fine, they are readily distributed over a large area by air currents.
The nuisance created by the solid particles in the air is dependent on
the size and physical characteristics of the individual particles. The
difficulty of catching the dust and cinder particles is principally a function
of the size and specific gravity of the particles.
Lower rates of combustion per square foot of grate area will reduce the
quantity of solid matter discharged from the chimney with the gases of
combustion. The burning of coke, coking coal, and sized coal from which
the extremely fine coal has been removed will not as a general rule produce
as much dust and cinders as will result from the burning of non-coking
coals and slack coal when they are burned on a grate.
Modern boiler installations are usually designed for high capacity per
square foot of ground area because such designs give the lowest cost of
construction per unit of capacity. Designs of this type discharge a
large quantity of dust and cinders with the gases of combustion, and if
pollution of the atmosphere is to be prevented, some type of catcher must
be installed.
NATURE'S DUST CATCHER
Nature has provided means for catching solid particles in the air and
depositing them upon the earth. A dust particle forms the nucleus for
each rain drop and the rain picks up dust as it falls from the clouds to the
earth. In fact, without dust in the air to form the nuclei for rain drops it
would never rain, and the earth would be continually enveloped in a
cloud of vapor. However, it was found in recent studies6 that rain was
not a good air cleaner of the material below about 0.7 micron.
•Atmospheric Pollution of American Cities for the years 1931-1933, by J. E. Ives et al (U. 5. Public
Health Bulletin No* 224. March, 1936).
CHAPTER 4. AIR POU.UTION
REFERENCES
Bulletin, Air Hygiene Foundation, Inc., Pittsburgh, Pa.
Determination and Control of Industrial Dust, by J. J. Bloomfield and J. M. Dalla
Valle (U. S. Public Health Bulletin, No, 217, 1935).'
Journal of Industrial Hygiene and Toxicology, Harvard School of Public Health,
Boston, Mass.
Reports of the National Silicosis Conference, Washington, D. C. To be published
by the U. S. Department of Labor.
Saranac Symposium on Silicosis, 1937, Saranac Laboratories, Saranac, N. Y.
Industrial Dust, by Philip Drinker and Theodore Hatch, McGraw Hill Co., N. Y.
Noxious Gases, by Y. Henderson and H. Haggard, Chemical Catalog Co., N. Y.
Occupation and Health, International Labour Office.
Preventive Medicine and Hygiene, by Milton J. Rosenau, D. Appleton- Century
Co., N. Y.
PROBLEMS IN PRACTICE
1 • Classify the detrimental aspects of air pollution as it affects large industrial
communities.
Air pollution may be classified (a) medical, as it affects the physiological functions of
people; (b) botanical, as it affects vegetation, trees, plants, shrubs and flowers; and (c)
physical, as it affects the discoloration and deterioration of buildings, and the nuisance
of soiled interior furnishings, clothes, merchandise, etc.
2 • Distinguish between dusts, fumes, and smokes.
Solid particles ranging in size from 1.0 micron to 150 microns are called dusts (micron =
Ms. ooo in.)-
Particles resulting from sundry chemical reactions and ranging from 0.1 to 1.0 micron in
size are called fumes.
Carbon particles less than 0.1 micron in size which generally arise from the incomplete
combustion of such materials as coal, oil, or tobacco are called smokes,
3 • What are some of the more important physical properties of these various
groups of foreign bodies which are of importance in ventilation?
In slowly moving air, dusts tend to settle out by gravity without agglomerating to form
larger particles; fumes have the tendency to form larger particles which will settle when
they attain the size of approximately 1.0 micron; while smokes tend to diffuse and remain
in the air as permanent impurities.
4 • Why is atmospheric pollution an important engineering problem?
a. Certain impurities, when present in too great concentrations, cause ill health or even
death.
b. High concentrations of solids occlude solar radiations.
c. Some materials cause permanent injury to parts of buildings, as sulphur fumes corrode
exposed metal.
d. Extra cleaning expense is incurred in dusty localities.
e. Internal combustion engines are damaged by abrasive dusts.
5 • How may the hazards of dust-producing industrial operations best be
curtailed?
By providing mechanical exhaust ventilation sufficient to keep dust concentration at a
safe level (see Table 3) and then removing foreign bodies to reduce the pollution of out-
side air.
87
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
6 • How may the pollution of the atmosphere he lessened?
By compelling industrial plants to install dust catching and smoke controlling devices.
In many cities the domestic heating plant is one of the most serious offenders, but these
plants are too small to justify the installation of dust catchers. Public education in
improved firing methods would be of considerable help in this field.
7 • What size particles are detrimental to health?
While fairly large particles may enter the upper air passages, those found in the lungs
are seldom more than 10 microns in size, and comparatively few of them are more than
5 microns. It is agreed that particles between % and 2 microns may be harmful; some
authorities place the upper limit at about 5 microns, and some incline to extend the
lower limit to 0.1 of a micron.
8 • Is the shape of the particle of any significance?
Hard particles with sharp corners or edges have a cutting effect on the delicate mucous
membranes of the upper respiratory tract which may lower the resistance of the nose and
throat to acute infections. This is aggravated by the irritating effects of some chemical
compounds which may be taken in with the air and which act to reduce resistance.
9 • What are the principal meteorological effects of smoke and dust?
a. The reduction in the amount of light received. Measurements have shown that
visible light may be as much as 50 per cent less intense in a smoky section of a city than
in a section that is free from smoke. Ultra-violet light is reduced as much or more, and
in some cases is cut out entirely for a time.
6. Smoke and dust aid in the formation and prolongation of fogs. City fogs accumulate
smoke and become darker in color and very objectionable. The sun requires a longer
time to disperse them, and when the water is evaporated, there is a rain of smoke and
soot particles that have been entrained.
10 • Why has not smoke abatement been more effective?
Because communities have not been made sufficiently aware of the possibilities of
burning high volatile fuels smokelessly and of separating cinder and ash from the stack
gases to a degree that will prevent a nuisance.
11 • Is the abatement of dust and cinders important?
Yes. Only a small percentage of the solid emission from stacks is smoke, in the accepted
popular sense; the remainder is fly-ash and cinders. While black smoke is disagreeable
and its tarry matter and carbon particles soil anything with which they come in contact,
the cinders and some of the ash are hard and destructive. They also, together with
dusts from industrial processes, make up the irritating, air-borne solids that are breathed
by individuals not working in a dusty mill or factory.
12 • Are air-borne impurities causative factors in hay fever, bronchial asthma,
and allergic disorders?
Yes. Recent medical investigations indicate that 90 per cent of seasonal hay fever and
40 per cent of bronchial asthma are caused by air-borne pollens, tree dusts, and other
allergic irritants.
13 • Name some essential requirements for the smokeless combustion of fuels.
Time, temperature, and turbulence. A study of these factors is usually of value in
overcoming a smoke nuisance.
14 • What is the Ringelmann Chart Method of comparing smoke densities?
See Chapter 44. The Ringelmann Chart consists of four cards ruled with lines having
different degrees of blackness. These cards, together with a white card and a black one,
are^hung in a horizontal row 50 ft from the observer. At this distance the lines become
invisible and the cards appear to be different shades of gray, ranging from white to black.
The observer, by matching the cards against the shades of smoke coming from a stack, is
able to estimate the blackness of the smoke as compared with the chart.
88
Chapter 5
HEAT TRANSMISSION COEFFICIENTS
AND TABLES
Methods o£ Heat Transfer, Coefficients, Conductivity of
Homogeneous Materials, Surface Conductance Coefficients,
Air Space Conductance, Practical Coefficients, Table of Con-
ductivities and Conductances, Tables of Over- all Coefficients
of Heat Transfer for Typical Building Construction, Combined
Coefficients of Transmission
IN order to maintain comfortable living temperatures within a building
it is necessary to supply heat at the same rate that it is lost from the
building. The loss of heat occurs in two ways, by direct transmission
through the various parts of the structure and by air leakage or filtration
between the inside and outside of the building. The purpose of this
chapter is to show methods of calculation and to give practical trans-
mission coefficients which may be applied to various structures to deter-
mine the heat loss by direct transmission. The amount lost by air
nitration is determined by different methods, as outlined in Chapter 6,
and must be added to that lost by direct transmission to obtain the total
heating plant requirements.
METHODS OF HEAT TRANSFER
Heat transmission between the air on the two sides of a structure takes
place by three methods, namely, radiation, convection and conduction.
In a simple wall built up of two layers of homogeneous materials separated
to give an air space between them, heat will be received from the high
temperature surface by radiation, convection and conduction. It will
then be conducted through the homogeneous interior section by con-
duction and carried across to the opposite surface of the air space by
radiation, conduction and convection. From here it will be carried by
conduction through to the outer surface and leave the outer surface by
radiation, convection and conduction. The process of heat transfer
through a built-up wall section is complicated in theory, but in practice
it is simplified by dividing a wall into its component parts and considering
the transmission through each part separately. Thus the average wall
may be divided into external surfaces, homogeneous materials and interior
air spaces. Practical heat transmission coefficients may be derived which
will give the total heat transferred by radiation, conduction and convec-
tion through any of these component parts and if the selection and method
of applying these individual coefficients is thoroughly understood it is
usually a comparatively simple matter to calculate the over-all heat
transmission coefficient for any combination of materials.
89
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
HEAT TRANSFER COEFFICIENTS
The symbols representing the various coefficients of heat transmission
and their definitions are as follows :
U = thermal^ transmittance or over-all coefficient of heat transmission ; the amount of
heat expressed in Btu transmitted in one hour per square foot of the wall, floor, roof or
ceiling for a difference in temperature of 1 deg F between the air on the inside and that
on the outside of the wall, floor, roof or ceiling.
k = thermal conductivity; the amount of heat expressed in Btu transmitted in one
hour through 1 sq ft of a homogeneous material 1 in. thick for a difference in temperature
of 1 deg F between the two surfaces of the material. The conductivity of any material
depends on the structure of the material and its density. Heavy or dense materials, the
weight of which per cubic foot is high, usually transmit more heat than light or less dense
materials, the weight of which per cubic foot is low.
C = thermal conductance; the amount of heat expressed in Btu transmitted in one
hour through 1 sq ft of a non-homogeneous material for the thickness or type under
consideration for a difference in temperature of 1 deg F between the two surfaces of the
material. Conductance is usually used to designate the heat transmitted through such
heterogeneous materials as plaster board and hollow clay tile.
/ =• film or surface conductance; the amount of heat expressed in Btu transmitted by
radiation, conduction and convection from a surface to the air surrounding it, or vice
versa, in one hour per square foot of the surface for a difference in temperature of 1 deg F
between the surface and the surrounding air. To differentiate between inside and outside
wall (or floor, roof or ceiling) surfaces, fi is used to designate the inside film or surface
conductance and /0 the outside film or surface conductance.
a — thermal conductance of an air space; the amount of heat expressed in Btu trans-
mitted by radiation, conduction and convection in one hour through an area of 1 sq ft of
an air space for a temperature difference of 1 deg F. The conductance of an air space
depends on the mean absolute temperature, the width, the position and the character of
the materials enclosing it.
R — resistance or resistivity which is the reciprocal of transmission, conductance,
or conductivity, i.e.:
-jj- - over-all or air-to-air resistance.
-T~ = internal resistivity.
TT — internal resistance,
c/
-j- — film or surface resistance.
1
— = air-space resistance.
As an example in the application of these coefficients assume a wall
with over-all coefficient U. Then,
H = AU(t-to) (1)
where
H = Btu per hour transmitted through the material of the wall, glass, roof or
floor.
A * area in square feet of wall, glass, roof, floor, or material, taken from building
plans or actually measured. (Use the net inside or heated surface dimensions
in all cases.)
- k = temperature difference between inside and outside air, in which t must always
be taken at the proper level. Note that t may not be the breathing-line
90
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
If the heat transfer between the air and the inside surface of the wall
is being considered, then,
H = A fi (t - h) f2)
where
fi = inside surface conductance.
t and h = the temperatures of the inside air and the inside surface of the wall re-
spectively.
In practice it is usually the over-all heat transmission coefficient that is
required. This may be determined by a test of the complete wall, or
it may be obtained from the individual coefficients by calculation. The
simplest method of combining the coefficients for the individual parts of
the wall is to use the reciprocals of the coefficients and treat them as
resistance units. The total over-all resistance of a wall is equal numeri-
cally to the sum of the resistances of the various parts, and the reciprocal
of the over-all resistance is likewise the over-all heat transmission coef-
ficient of the wall. For a wall built up of a single homogeneous material
of conductivity k and x inches thick the over-all resistance,
If the coefficients /i,/0 and k, together with the thickness of the material
x are known, the over-all coefficient U may be readily calculated as the
reciprocal of the total heat resistance.
For a compound wall built up of three homogeneous materials having
conductivities AI, &2 and ks and thicknesses xi, xz and x$ respectively, and
laid together without air spaces, the total resistance,
l=!+i+t+t+i
For a wall with air space construction consisting of two homogeneous
materials of thicknesses Xi and x2 and conductivities ki and kz, respectively,
separated to form an air space of conductance a, the over-all resistance,
-L - — 4- -5- 4-—+ -5-4- 1 ' m
U ' fi + ft, + a + k, + 7T 5
Likewise any combination of homogeneous materials and air spaces can
be put into the wall and the over-all resistance of the combination may be
calculated by adding the resistances of the individual sections of the wall.
In certain special forms of construction such as tile with irregular air
spaces it is necessary to consider the conductance C of the unit as built
instead of the unit conductivity k, and the resistance of the section is
equal to -pr. The method of calculating the over-all heat transmission
o
coefficient for a given wall is comparatively simple, but the selection of
the proper coefficients is often complicated. In some cases the construc-
tion of the wall is such that the substituting of coefficients in the accepted
formula will give erroneous results. This is the case with irregular cored
91
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
out air spaces in concrete and tile blocks, and walls in which there are
parallel paths for heat flow through materials having different heat
resistances. In such cases it is necessary to resort to test methods to
check the calculations, and in practically all cases it has been necessary
to determine fundamental coefficients by test methods.
Conductivity of Homogeneous Materials
The thermal conductivity of homogeneous materials is affected by
several factors. Among these are the density of the material, the amount
of moisture present, the mean temperature at which the coefficient is
determined, and for fiberous materials the arrangement of fiber in the
material. There are many fiberous materials used in building construc-
tion and considered as homogeneous for the purpose of calculation,
whereas they are not really homogeneous but are merely considered so as a
matter of convenience. In general, the thermal conductivity of a material
increases directly with the density of the material, increases with the
amount of moisture present, and increases with the mean temperature at
which the coefficient is determined. The rate of increase for these various
factors is not the same for all materials, and in assigning proper coef-
ficients one should make certain that they apply for the conditions under
which the material is to be used in a wall. Failure to do this may result
in serious errors in the final coefficients.
Surface Conductance Coefficients
Heat is transmitted to or from the surface of a wall by a combination
of radiation, convection and conduction. The coefficient will be effected
by any factor which has an influence on any one of these three methods of
transfer. The amount of heat by radiation is controlled by the character
of the surface and the temperature difference between it and the sur-
rounding objects. The amount of heat by conduction and convection is
controlled largely by the roughness of the surface, by the air movement
over the surface and by the temperature difference between the air and
the surface. Because of these variables the surface coefficients may be
subject to wide fluctuations for different materials and different con-
ditions. The inside and outside coefficients jfi and/0 are in general affected
to the same extent by these various factors and test coefficients deter-
mined for inside surfaces will apply equally well to outside surfaces under
like conditions. Values for /i in still and moving air at different mean
temperatures have been determined for various building materials at the
University of Minnesota under a cooperative agreement with the Society.1
The relation obtained between surface conductances for different
materials at mean temperatures of 20 F is shown in Fig. 1. These values
were obtained with air flow parallel to the surface and from other tests in
which the angle of incident between the direction of air flow and the
surface was varied from zero to 90 deg it would appear that these values
might be lowered approximately 15 per cent for average conditions.
While for average building materials there is a difference due to mean
temperature, the greatest variation in these coefficients is caused by the
character of the surface and the wind velocity. If other surfaces, such as
'Surface Conductances as Affected by Air Velocity, Temperature and Character of Surface, by F. B.
Rowley, A. B. Algren and J. L. Blackshaw (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 429).
92
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
aluminum foil with low emissivity coefficients were substituted, a large
part of the radiant heat would be eliminated. This would reduce the
total coefficient for all wind velocities by about 0.7 Btu and would make
but very little difference for the higher wind velocities. In many cases in
building construction the heat resistance of the internal parts of the wall
is high as compared with the surface resistance and the surface factors
become of small importance. In other cases such as single glass windows
the surface resistances constitute practically the entire resistance of the
structure^ and therefore become important factors. Due to the wide
variation in surface coefficients for different conditions their selection for
15 20 25
AIR VELOCITY, M. P. H.
FIG. 1. CURVES SHOWING RELATION BETWEEN SURFACE CONDUCTANCES FOR
DIFFERENT SURFACES AT 20 F MEAN TEMPERATURE
a practical building becomes a matter of judgment. In calculating the
over-all coefficients for the walls of Tables 3 to 12, 1.65 has been selected
as an average inside coefficient and 6.0 as an average outside coefficient
for a 15-mile wind velocity. In special cases where surface coefficients
become important factors in the over-all rate of heat transfer more
selective coefficients may be required,
Air Space Conductance
Heat is conducted across an air space by a combination of radiation,
conduction and convection. The amount of heat by radiation is governed
largely by the nature of the surface and the temperature difference
between the boundary surfaces of the air space. Conduction and con-
93
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
vection are controlled largely by the width and shape of the air space and
the roughness of the boundary surfaces. The thermal resistances of air
spaces bounded by extended parallel surfaces perpendicular to the
direction of heat flow and at different mean temperatures have been
determined for average building materials at the^ University of Minnesota
in a cooperative research program with the Society.
The values given in Table 1 show the results of this study and apply to
air spaces bounded by such materials as paper, wood, plaster, etc.,
having emissivity coefficients of from 0.9 to 0.95. The conductivity
coefficients decrease with air space width until a width of about % in. has
been reached, after which the width has but very little effect. In these
TABLE 1. CONDUCTANCES OF AIR SPACES a AT VARIOUS MEAN TEMPERATURES
MIAN
COITOUCTANCZS or AIR SPACES FOR VARIOUS WIDTHS IN INCHES
TBMP
DBG FAHR
0.128
0.250
0.364
0.493
0.713
1.00
1.500
20
2.300
1.370
1.180
1.100
1.040
1.030
1.022
30
2.385
1.425
1.234
1.148
1.080
1.070
1.065
40
2.470
1.480
1.288
1.193
1.125
1.112
1.105
50
2.560
1.535
1.340
1.242
1.168
1.152
1.149
60
2.650
1.590
1.390
1.295
1.210
1.195
1.188
70
2.730
1.648
1.440
1.340
1.250
1.240
1.228
80
2.819
1.702
1.492
1.390
1.295
1.280
1.270
90
2.908
1.757
1.547
1.433
1.340
1.320
1.310
100
2.990
1.813
1.600
1.486
1.380
1.362
1.350
110
3.078
1.870
1.650
1.534
1.425
1.402
1.392
120
3.167
1.928
1.700
1.580
1.467
1.445
1.435
130
3.250
1.980
1.750
1.630
1.510
1.485
1.475
140
3.340
2.035
1.800
1.680
1.550
1.530
1.519
150
3.425
2.090
1.852
1.728
1.592
1.569
1.559
^Thermal Resistance of Air Spaces by F. B. Rowley and A. B. Algren (A.S.H.V.E. TRANSACTIONS,
Vol. 35, 1929, p. 165).
coefficients radiation is a large factor, and if surfaces with low emissivity
coefficients are substituted for ordinary building materials the total
amount of radiant heat will be reduced. The reduction in radiant heat
caused by the low emissivity surface is independent of width of air space.
Air spaces properly formed in combination with metallic surfaces such as
aluminum foil, coated sheet steel, and other materials having a reflective
surface, possess heat repelling characteristics. Values of air spaces
lined with aluminum foil on one or both sides for widths of % in. and % in.
are shown in Table 2 of conductivities. A low emissivity coefficient is
dependent on the permanency of the reflective surface. If a bright clean
surface is covered with a thin layer of corrosive material its reflectivity is
appreciably reduced2.
In comparing the conductance coefficients for air spaces with and with-
out bright metallic surface lining it should be noted that the reduction in
heat transfer is substantially as great when one surface is lined as it is
when both surfaces are lined. The reason for this is that practically
95 per cent of the total radiant heat is intercepted by one surface lining
^Aluminum Foil Insulation (National Bureau of Standards Letter Circular No. LC465. June, 1936).
94
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
and there is but a small amount left to be stopped by the second surface
lining. The effect of any low emissivity surface in 'stopping the trans-
mission of radiant heat is the same regardless of whether it is on the high
or low temperature side of the air space. For materials such as aluminum
paint or bronze paint which stop only a small percentage of radiant heat
there is a greater percentage of gain by addition of a second surface lining.
PRACTICAL COEFFICIENTS
For practical purposes it is necessary to have average coefficients that
may be applied to various materials and types of construction without
the necessity of making tests on the individual material or combination of
materials. In Table 2 coefficients are given for a group of materials which
have been selected from various sources. Wherever possible the proper-
ties of material and conditions of tests are given. However, in selecting
and applying these values to any construction a reasonable amount of
caution is necessary; variations will be found in the coefficients for the
same materials, which may be partly due to different test methods used,
but which are largely due to variations in materials. The recommended
coefficients which have been used for the calculation of over-all coefficients
as given in Tables 3 to 12 are marked by an asterisk.
It should be recognized in these tables of calculated coefficients that
space limitations will not permit the inclusion of all the combinations of
materials that are used in building construction and the varied applications
of insulating materials to these constructions. Typical examples are given
of combinations frequently used, but any special construction not given in
Tables 3 to 12 can generally be computed by using the conductivity values
given in Table 2 and the fundamental heat transfer formulae. For
example, the tabulation of all of the values for multiple layers of insulating
materials would present extensive and detailed problems of calculations
for the varied application combinations, but the engineer having the
fundamental conductivity values can quickly obtain the proper coefficients.
Attention is called to the fact that the conductivity values per inch of
thickness do not afford a true basis for comparison between insulating
materials as applied, although they are frequently used for that purpose.
The value of an insulating material is measured in terms of its heat
resistance, which not only depends upon the thermal conductivity coef-
ficient per inch but also upon the thickness as installed and the manner, of
installation. For instance the material having a coefficient of 0.50 and
1 in. thick is equal in value to a material having a coefficient of 0.25 and
a thickness of J^ in. Certain types of blanket installations are designed
to be installed between the studs of a frame building in such manner as to
give two air spaces. In order to get the full value of such materials they
should be so installed that each air space is approximately 1 in. or more
in thickness and the air spaces should be sealed at the top and bottom to
prevent the circulation of air from one space to the other. Another
common error in installing such a material is to nail the blanket on the
outside of the studs underneath the sheathing, in which case one air
space is lost and also the thickness of the insulating material is materially
reduced at the studs. There are certain other types of insulation which
are very porous, allowing air circulation within the material if not
95
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
properly installed. The architect or engineer must carefully evaluate the
economic considerations involved in the selection of an insulating material
as adapted to various building constructions. Lack of good judgment in
the intelligent choice of an insulating material, or its improper installation,
frequently represents the difference between good or unsatisfactory
results. Refer to Chapter 7 for a discussion of wall condensation.
Computed Transmission Coefficients
Computed heat transmission coefficients of many common types of
building construction are given in Tables 3 to 13, inclusive, each con-
struction being identified by a serial number. For example, the coefficient
of transmission (IT) of an 8-in. brick wall and J^ in. of plaster is 0.46, and
the number assigned to a wall of this construction is 1-B, Table 3.
Example L Calculate the coefficient of transmission (IT) of an 8-in. brick wall with
J£ in. of plaster applied directly to the interior surface, based on an outside wind exposure
of 15 mph. It is assumed that the outside course is of hard (high density) brick having a
conductivity of 9.20, and that the inside course is of common (low density) brick having
a conductivity of 5.0, the thicknesses each being 4 in. The conductivity of the plaster is
assumed to be 3.3, and the inside and outside surface coefficients are assumed to average
1.65 and 6.00, respectively, for still air and a 15 mph wind velocity.
Solution, k (hard high density brick) - 9.20; x = 40 in.; k (common low density
brick) = 5.0; x « 4.0 in.; k (plaster) = 3.3; * = M in.;/i = 1.65;/0 - 6.0. Therefore,
6.0 T 9.20 ^ 5.0 ~*~ 3.3 "*" 1.65
^ 1
0.167 + 0.435 -i- 0.80 + 0.152 + 0.606
« 0.46 Btu per hour per square foot per degree Fahrenheit difference in tempera-
ture between the air on the two sides.
The coefficients in the tables were determined by calculations similar
to those shown in Example 1, using Fundamental Formulae 3, 4 and 5
and the values of k (or C),/i, /0 and a indicated in Table 2 by asterisks.
In computing heat transmission coefficients of floors laid directly on the
ground (Table 10), only one surface coefficient (/i) is used. For example,
the value of U for a 1-in. yellow pine floor (actual thickness, 25/32 in.)
placed directly on 6-in. concrete on the ground, is determined as follows :
1
U = ~~; :rir: — = 0.48 Btu per hour per square foot per degree difference
I , U. fol , O.U
1.65 •" 0.80 12.62
in temperature between the ground and the air immediately above the floor.
Rigid insulation refers to the so-called board form which may be used
structurally, such as for sheathing. Flexible insulation refers to the
blankets, quilts or semi-rigid types of insulation.
Actual thicknesses of lumber are used in the computations rather than
nominal thicknesses. The computations for wood shingle roofs applied
over wood stripping are based on 1 by 4 in. wood strips, spaced 2 in. apart.
Since no reliable figures are available concerning the conductivity of
Spanish and French clay roofing tile, of which there are many varieties,
the figures for such types of roofs were taken the same as for slate roofs, as
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
TABLE 2. CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING
MATERIALS AND INSULATORS**
The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness,
unless otherwise indicated.
Material
Description
DENSITY
(La PER Cu FT)
MEAN TEMP.
(DKG FAHR)
CoNDDcrivrrr (K)
OR
CONDUCTANCE (C')
~l-« _,jo
>• 8
5 3
|
<J
Cement
Fine
Aggre-
0-No. 4
Coarse
*gj" Slump
No.4-H
Per
Cent
Voids
SAND AND GRAVEL,
CONCRETE—
1
1
2.00
2.75
3.50
2.00
2.00
2.75
2.75
3.50
3.50
2.75
4.50
5.50
2.75
2.75
4.50
4.50
5.50
5.50
0
8
1
11.5
10.9
11.2
13,9
13.9
14.6
14.6
14.7
14.7
144.7
145.7
144.5
142.5
142.5
141.1
141.1
139.2
139.2
142.3
75.06
74.77
75.00
75.50
74.74
73.30
74.89
74.50
75.15
13.10
12.90
13.20
12.10
12.40
12.40
12.10
12.85
12.50
12.62*
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
1
4)
4)
4)
4)
4)
4)
4)
4)
t!
(4)
Avg. Value for Sand and Gravel Concrete
LlMBSTONE CONCBETB
1
1
1
1
1
1
2.00
2.75
3.50
2.00
2.75
3.50
2.75
4.50
5.50
2.75
4.50
5.50
0
0
0
3
3
16.6
15.4
16.3
20.9
23.4
23.4
135.3
137.8
136.4
130.1
126.0
127.3
132.15
74.87
75.18
74.75
74.85
74.45
75.26
11.20
12.00
11.50
10.50
10.00
9.79
10.83
1 0.09
0.08
0.09
0.10
0.10
0.10
Avg. Value for Limestone Co
ncfftte
CINDBR CONCRETE
1
1
1
1
1
1
2.00
2.75
3.50
2.00
2.75
3.50
2.75
4.50
5.50
2.75
4.50
5.50
0
0
0
3
3
3
18.2
19.9
21.4
22.8
26.0
24.4
103.6
98.7
92.0
101.4
94.0
94.4
97.35
75.26
75.71
75.72
74.95
75.20
75.55
4.63
4.30
3.73
4.89
4.38
4.24
4.86
0.22
0.23
0.27
0.20
0.23
0.24
4)
I
4)
4)
Avg. Value for Cinder Concrt
>te
HATDITE ,„.
1
1
1
1
1
1
1
2.00
2.75
3.50
2.00
2.75
2.75
3.50
2.75
4.50
5.50
2.75
4.50
4.50
5.50
0
0
0
4
4
4
4
18.0
19.8
21.8
21.2
22.2
22.2
23.9
80.7
75,0
71.7
78,8
72.4
72.4
71.0
74.57
74.82
75.75
74.82
74.76
75.39
75.49
75.46
4.15
3.78
3.67
4.38
3.89
3.86
4.00
3.96
0.25
0.26
0.27
0.23
0.26
0.26
0.25
4)
4)
3
3
4)
Avg. Value f or Haydite ,
AUTHORITIES:
JU. S. Bureau of Standards, tests based on samples submitted by manufacturers.
'A. C. Willard, L. C. Lichty, and L. A. Harding, tests conducted at the University of Illinois.
*J. C. Peebles, tests conducted at Armour Institute of Technology, based on samples submitted by
manufacturers.
*F. B. Rowley, tests conducted at the University of Minnesota.
5A.S.H.V.E. Research Laboratory.
•E. A. Allcut, tests conducted at the University of Toronto.
'Lees and Charlton.
8G. B. Wilkes, tests conducted at the Massachusetts Institute of Technology.
*Recommended conductivities and conductances for computing heat transmission coefficients.
tFor thickness stated or used on construction, not per 1-in. thickness.
«For additional conductivity data see Chapters 3 and 15, 1937 A.S.R.E. Data Book.
klf outside surface of block is painted with an impervious coat of paint, add 0.07 to resistance for sand
and gravel blocks. Add 0.18 to resistance for cinder blocks. Add 0.17 to resistance for haydite blocks.
"Recommended value. See Heating, Ventilating and Air Conditioning, by Harding and Willard, revised
edition, 1932.
dSee A.S.H.V.E. Research Paper, Conductivity of Concrete, by F. C. Houghten and Carl Gutberlet
(A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 47).
<The 6-in., 8-in.t and 10-in. hollow tile figures are based on two cells in the direction of heat now. The
12-in. hollow tile is based on three cells in the direction of heat flow. The 16-in. hollow tile consists of one
10-in. and one 6-in. tile, each having two cells in the direction of heat flow.
"Roofing, 0.15-in.* thick (1.34 Ib per SQ ft), covered with gravel (0.83 Ib per sq ft), combined thickness
assumed 0.25.
• ASurface values were obtained on vertical surfaces and varying with the temperature differences. A
foil lined air space in a horizontal position will have a coefficient roughly three times greater if the heat
flow is upward rather than downward.
97
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2. CONDUCTIVITIES \k) AND CONDUCTANCES (C) OF BUILDING
MATERIALS AND INSULATORS— Continued
The coeficients are expressed in Biu per hour per square foot per degree Fahrenheit per 1 in. thickness
unless otherwise indicated.
Material
Description
DENSITY
(LB PER Cu FT)
IMEAN TEMP.
(DEQ FAHR)
CONDUCTIVITY (fc)
OR
CONDUCTANCE (C)
g g
hi
EH
1
Fine Coarse per
• O-No. 4 No. 4-J^ , 01
EXPANDED BUBNED CLAY 1 , 8.00 18.4
STBAJC TREATED LIMESTONE SLAG- j 1 ; 7.00 27.1
PUIIICI; MTNED TN CAT.TF 1 ; 8.00 26.5
57.9
74.6
65.0
75.57
74.49
74.68
2.28
2.27
2.42
0.44
0.44
0.41
(4)
(4)
(4)
BY-PHODUCT OF MANUFACTURE ' 1 ,8.00 Modulus 25.5
OF PHOSPHATES ' 1 1 8.00 3.75 21.1
86.6
91.1
74.62
74.43
3.19
3.42
0.31
0.29
(4)
(4)
HATDIT
1 j 8.50 21.8
1 i 8.50 21.8
67.1
67.1
75.89
74.60
2.89
2.815
0.35
0.34
(4)
(4)
f • l « 16 l-w* CM cwwTfft ttocn
Sand and v 1 te
126.4
40
40"~
40
40
40"'
40
40
40
40
0.900
1.000
0.560
0.856
0.577
0.600
0.390
0.250
0.266
0.495
0.206
\
F
•*
,*
*
*
*
l.ll
1.00
1.79
1.17
1.73
1.66
2.56
4.00
3.76
2.02
4.85
(4)
2
4)
ti
4)
t!
i!
Sand and gravel aggregate used for calcu-
lations _
a- ]•
^j ^JL*
At
Cores filled with 5. 14 Ib density cork
Crushed limestone aggregate
134.3
86.2
Cinder aggregate ,_ ,
Cinder aggregate used for calculations— ~
Cores filled with 69.7 Ib density cinders
Cores filled with 5 . 12 Ib density cork-
J5J-
Cores filled with U.2 Ib density rock wool
TIftydite aggregate
67.7
Cores MeJTwith 5.06 Ib density cork
8>12
,,63.c*~« <*«**>
*«>',
Sand and gravel aggregate..™ „_
Sand and gravel aggregate used for calcu-
lations i , . - „
124.9
40
0.777f
O.SOOf*
0.531f*
0.237f*
0.468f
0.168f*
1.29
1,88
4.22
2.13
5.94
(4)
4)
tl
4)
4)
->}
L
Or
1
x_S*- '
If
T,
Cinder aggregate— ~—~-.—.-~..~— _...__..
Cores filled with 5.24 Ib density cork.
86.2
__,
40
40
40
40
Cores filledwith 5 .6 Ib density cork.
.5f -f
-.jvrf
Cinder aggregate-
Double waU with 1 in. air space between
1 in. space filled with 9.97 ID density rock wool
100.0
100.0
100.0
40
40
40
l.OOOf
0.358f
0.204f
1.00
2.70
4.90
4)
4)
4)
(4)
!>
— j run r~
= > i
, .s, ,
,.n *_
5x8x12 block sand and gravel aggregate™.
133.7
40
0.380f
2.6.?
JJ'^^E
gtjij
iin^1^
-rH*
1
-,*-•*-, -"
5x8x12 block sand and gravel aggregate*..
134.0
40
0.947f
1.06
(4)
Ti!
ilT
m
u»
For notes see Page 97.
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
TABLE 2.
CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING
MATERIALS AND INSULATORS — Continued
The coefficients are expressed in Btu per hour per square jopt per degree Fahrenheit per 1 in. thickness,
unless otherwise indicated.
Material
Description
DENSITY
(LB PER Cu FT)
II
li
CONDUCTIVITY (Jt)
OR
CONDUCTANCE (C')
-M'rf* -T'O
T.T
3 «
t«
-aj
MASONRY MATERIALS
Low density
5.00*
9.20*
5.00*
12.00*
ll.SSfo1
16.36
1.06
1.44
1.80
2.18
1.66*
3.98
12.50*
12.00*
i.oot*
0.64f*
0.60f*
0.58f*
0.40f*
0.31t*
i.oot
0.60t
0.47t
0.46t*
1.66
2.96
12.00*
0.20
0.11
0.20
0.08
0.94
0.69
0.56
0.46
0.60
0.25
0.08
0.08
1.00
1.57
1.67
1.72
2.50
3.23
1.00
1.67
2.13
2.18
0.60
0.34
0.08
(5
1
(3)
(3)
(3)
(4)
(3)
High density
75
75
75
75
74
70
Damp or wet
CEMENT MORTAR. —
CONCRETE
STONE
SrrjCCO _ _
TILE.
Typical . . - —
40.0
50.0
60.0
70.0
51.2
101.0
Various ages and mixes'' .
Cellular
Cellular_
Cellular ..
Cellular
Typical fiber gypsum, 87.5% gypsum and
12.5% wood chips
Special concrete made with an aggregate of
hardened clay~—l-2~3 mix_-,..~
Typical- .
Typical ..
Typical hollow clay 4 in.)
TILE OR TBHRAZZO
Typical hollow clay 6 in.)*
Typical hollow clay 8 in.)* _ - ..- —
Typical hollow clay 10 in.)" -
Typical hollow clay 12 in,)*
Typical hollow clay 16 in,)* —
no"
100
105
"70"
76
(2)
8
@
Hollow clay (2 in.)H-in. plaster both sides —
Hollow clay (4 in.) J^-in. plaster both sides —
Hollow clay (6 in.) l/fcaa. plaster both sides. —
Hollow gypsum (4 in.) _
Solid gypsum _
Solid gypsuin_—..- - —
Typical flooring-
120.0
127.0
124.3
YlT
75.6
INSULATION— BLANKET
OR FLEXIBLE TYPES
FlBlR-
Typical
3.62
4.60
3.40
4.90
5.76
7.70
11.00
1.00
6.70
12.1
70
90
90
90
71
71
75
90
75
75
0.27*
0.25
0.26
0.25
0.28
0.26
0.28
0.25
0.24
0.25
0.40t
3.70
4.00
3.85
4.00
3.57
3.85
3.57
4.00
4.17
4.00
2.50
(3)
1)
1)
(1)
(3)
(3)
@
(3)
(4)
Chemically treated wood fibers held between
layers of strong pjiper/.,.. _ -.„- - -
Eel grass between strong paper/
Flax fibers between strong paper/.
Chemically treated hog hair between kraf t
paper/ —
Chemically treated hog hair between kraft
paper and asbestos pap?!1/ „ - -
Hair felt between layers "of paper/
Kapok between burlap or paper/
Jute fiber/ ... .
Ground paper between two layers, each %-in.
thick maae up of two layers of kraft paper
(sample %-in. thick) —
INSULATION— SEMI-
RIGID TYPE
FlBBR
Felted cattle h^>/
13.00
11.00
12.10
13.60
7.80
6.30
6.10
6.70
10.00
11.00
90
90
70
90
90
90
90
75
90
70
0.26
0.26
0.30
0.32
0.28
0.27
0.26
0.25
0.37
0.26
3.84
3.84
3.33
3.12
3.57
3.70
3.85
4.00
2.70
3.84
1)
1)
1)
i
i)
3)
K UK
Flax/ . — — - -
Flax and rye/
Felted hair and asbestos/ -
75% hair and 25% jute/
50% hair and 50% jute/ .. _
jute/ "' ._ ._
Felted jute and asbestos/ - .
Compressed peat moss
INSULATION—LOOSE
FILL OR BAT TYPE
"BY*™*
Made from ceiba fibers/
a « a « ^
1.90
1.60
75
75
0.23
0.24
4.35
4.17
(3)
(3)
For notes see page 97.
99
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2. CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING
MATERIALS AND INSULATORS — Continued
The efficients are expressed in Btu fer hour per square foot per degree Fahrenheit per 1 in. thickness,
unless otherwise indicated.
Material
Description
DENSITY
(Ln PER Cu FT)
MEAN TEMP.
(DBG FAHR)
CONDUCTIVITY (fc)
OR
CONDUCTANCE (C)
~ js ^|O
g Y E
|si 1
S S 5
INSLT.ATION -LOOSE
FILL OR BAT TYPE
—Continued
GLASS Wool
GRANULAR.
Fibrous material made from dolomite and
silica.— .... i •
1.50
9.40
1.50
4.20
6.20
30.00
24.00
18.00
12.00
34.00
26.00
24.00
19.80
18.00
ITlO
21.00
18.00
14.00
10.00
14.50
14.50
11.50
12.00
8.80
13.20
3.00
75
103
75
72
42
90
90
90
90
90
90
75
90
75
90
90
90
90
90
77
75
72
90
90
90
90
0.27
0.27
0.27
0.24
0.32
1.00
0.77
0.59
0.44
0.60
0.52
0.48*
0.35
0.34
0.27*
0.31
0.30
0.29
0.28
0.27*
0.33
0.38
0.31
0.41
0.41
0.36
0.31
3.70 (3)
3.70 (1)
3.70 (3)
4.17 (3)
3.12 3)
.00 1)
.30 1
.69 1
.27 1
.67 1
.92 1
2.08 3)
2.86 1)
2.94 3)
3.70 _
3.22 1)
3.33 1
3.45 1
3.57 1)
3.70 1)
3.03 1)
2.63 3)
3.22 3)
2.44 1
2.44 1
2.78 1)
3.22 1)
Fibrous material made from slag
Fibrous material 25 to 30 microns in dia-
meter, made from virgin bottle glass
Made from combined silicate of lime and
alumina
MINERAL WOOL.
RlORANULATZD COBK
ROCK WOOL
Made from expanded aluminum-magnesium
silicate
Cellular dry
« u
ti a.
Flaked dry and fluffy-'
pjasea, ary ana nuny
a u u u
u u u u
u u * u
All forms typical t
About 3to-in particles
Fibrous material made from rock .
SAWDUST^., ^ t _, T
It U U U U
ff u ft u a
tt It U « It
Rock wool with a binding agent
Rock wool with flax, straw pulp, and binder
Rock wool with vegetable fibers
Various ,
SHAVTWGS
Various from planer
From maple, beech and birch (coarse)
Redwood bark
INSULATION— RIGID
FEBBB „„
Typical
14760
10.60
7.00
5.40
14.50
10.00
15.00
17.90
15.20
54.00
16.10
19.30
24.20
13.50
13.80
17.00
15.90
15.00
90
90
90
90
90
75
71
78
70
75
81
86
72
70
70
68
72
70
52
72
0.30*
0.34
0.30
0.27
0.25
0.32
0.33*
0.28
0.33
0.36
0.32
1.07f
0.34
0.51
0.46
0.33
0.30
0.33
0.33
0.33
0.33
0.29
0.33
0.34
3.33 -
2.94 (1)
3.33 (1)
3.70 (1)
4.00 (1)
3.12 (1)
3.03 ._
3.57 3)
3.03 3)
3.12 4)
3.12 3)
0.93 3)
2.94 3
1.96 1
2.17 3)
3.03 3)
3.33 3
3.03 3
3.03 3
3.03 3)
3.03 6)
3.45 3)
3.03 3)
2.94 (1)
No added binder
tt a u
UK u
it it it
Asphaltic binder .._. ._.
Typical
Chemically treated hog hair covered with
film of asphalt
Madfl from 1*1171 staHn?
• " exploded wood fibers
• tt hard wood fibers
Insulating plaster 9/10-in. thick applied to
£|-in. plaster board base
M?M?e from licorice roots
Made from 85% magnesia and 15% asbestos
Made from shredded wood and cement
" a sjigar nans fiber, JL .
Sugar cane fiber insulation blocks encased in
asphalt membrane
Made from wheat straw --,,-,-,,
« wnnd fiber
«
B
*
8.50
15.20
16.90
«
u
90
BUILDING BOARDS
\SR-Kfrrnx
123.00
20.40
86
110
2.70
0.48
0.37 (1)
2.08 (2)
Corrugated asbestos board
For notes see Pa^e 97.
100
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
TABLE 2. CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING
MATERIALS AND INSULATORS— Continued
The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness
unless otherwise indicated.
Material
Description
DENSITY
(La PER Cu FT)
MBAN TBMP.
(DEQ FAHR)
CONDUCTIVITY (fc)
OR
CONDUCTANCE (C)
~ \** ~ !cj
i i
«!
BUILDING BOARDS
—Continued
ASBESTOS ~
Pressed asbestos mill board _
Sheet MhfiRtns
60.50
48.30
86
110
0.84
0.29
1.19
3 45
(1)
?)
GYPSUM—— -...—
Gypsum between layers of heavy paper
Rigid, gypsum between layers of heavy
paper (H-in. thick)
62.80
53.50
70
90
1.41
2.60f
0.71
0.38
3)
(1)
PLASTER BOARD.._ _ „.
Gypsum muted with sawdust between layers
of heavy paper (0.39-in. thick)
(*$ in )
60.70
90
3.60f
3.73J*
0.28
0.27
(1)
(fcin.) -
—
2.82f*
0.35
-
ROOFING CONSTRUCTION
ROOTING . -
Asphalt, composition or prepared
70 00
75
6 50t*
0 15
0)
Built up-— iNP11 tniftk *" *"
3.53f*
0.28
Built up, bitumen and felt, gravel or slag
snrfaftftdff T T T
1.33
0.75
(2)
Plaster board, gypsum fiber concrete and
3-ply roof roaring ?V£ i^ thick
52 40
76
0.58f
1.72
4)
SHTNGT/I&S — -^ -.
AaWWi
65.00
75
6.00f*
0.17
3)
A«trhfl.|t
70.00
75
6.50t*
0.15
3)
RlfttA
201.00
10.37*
0 10
7)
Wood
1.28f*
0.78
PLASTERING MATERIALS
PLASTER
foment
8.00
0.13
(?)
Gyp?UTn typififtl
3.30*
0.30
Thifi1rr,P*s 3^ in
73
8.80t
0.11
(4)
METAL T,ATW ^NP PT.ASTTB^
Total thielcnfisa % in.
4.40t*
0.23
WOOD LATH AND PLASTER
54-in. plaster, total thickness % in
70
2. 50t*
0.40
(4)
BUILDING
CONSTRUCTIONS
FBAMD-
1-in, fir sheathing and buiMing paper
30
0.71t*
1.41
(4)
1-in. fir sheathing, building paper, and
20
O.SOf*
2.00
(4)
1-in. fir sheathing, building paper and stucco
Pine lap siding and building paper-~siding
4 in wi^e , !,
20
16
0.55
O.SSf*
1.82
1.18
(4)
(4)
Yellow pine tap siding. .--
1.28t*
0.78
FLOORING ._ -
Maple — across grain..^_ .. , ^1J..,
40.00
75
1.20
0.83
(3)
Bfttt'fisnip linoleum (M-"1 ) "
1.36f*
0.74
AIR SPACE AND SURFACE
COEFFICIENTS
Am ftPAdftH
Over %-in. faced with ordinary building
materials
40
I.IO"*
0.91
(4)
SURFACES, ORDINARY
fitill »ur (/i)
1.6St*
0.61
(4)
15 mph — (/o) . ,«..... , ,-
6. 00-*
0.17
(4)
SURFACE ROUGH STUCCO
p.oot*
0.11
(4)
SURFACE, BRIGHT ALTTMTVTTM
Still 9)f (/i)11
o.sot
1.25
(«)
AIR SPACES FACED WITH
BRIGHT ALUMINUM
FOIL
Air space, faced one side with bright alumi-
num foil over M-"1- win"fc
50
0.46f*
2.17
(4)
Air space, faced one side with bright alumi-
num foil iHj-in wide
50
0 62t
1.61
(4)
Air space,' faced both sides. with bright
aluminum foil, over %-in. wido , .,
Air space, faced both sides with bright
aluminum foiL ^-in wiH^,rT, T
50
50
0.41f*
O.S7f
2.44
1.75
(4)
(4)
For notes see Page 97.
101
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2. CONDUCTIVITIES (A) AND CONDUCTANCES (C) OF BUILDING
MATERIALS AND INSULATORS — Continued
The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness,
unless otherwise indicated.
Material
Description
DBNBPrr
(La PER Cu FT)
LMEAN TEMP.
(Duo FAHR)
CONDUCTIVITY (Jk)
OR
CONDUCTANCE (C)
H* -<|o
AIR SPACES FACED WITH
BRIGHT ALUMINUM
FOIL—Continued
Air space divided in two with single curtain
of bright aluminum foil (both sides bright)
Each space over ?^i"in wide
50
0.23f*
4.35 (4)
Each gp&ce J^o-in. wide . . ,.,..,
SO
0.31f
3.23 (4)
Air space with multiple curtains of bright
aluminum foil bright on both sides,
curtains more than %-in. apart, ah* circu-
lation between spaces prevented:
2 curtains fonnjpg 3 npfurflfi
50
O.lSf*
6.78 (4)
3 curtains forming 4 spaces
50
O.llf*
9.22 (4
4 curtains forming 5 spaces L-.L^,,r
50
0.09f*
11.66 (4
SPACES FACED WITH NOX-
METALLIC REFLECTIVE
SURFACE
Fabric with non-metallic reflective surface
06 in. thick) placed in center of a 1M in-
ftir spare
70
0.33f
3.03 (4)
Core o'f fiber board coated two sides with
non-metallic reflective surface (% in.
thick) placed in space having approxi-
mately % in. air space on each side
Fiber board coated one side with non-
metallic reflective surface (% in. thick)
placed in space having approximately
*•£ in air space on each side
23.4
70
75
0.27f
0.49f
3.70 (3)
2.04 (3)
Air space divided in two with fabric faced
both sides with non-metallic reflective
surface, each space over %-in. wide
Air space over J^-in. wide faced one side
with non-metallic reflective surface
40
40
0.33f
0.67f
3.03 (4)
1.49 (4)
WOODS (Across Grain)
RA.TJU
20.0
90
0.58
1.72 (1)
8.8
90
0.38
2.63 )
7.3
90
0.33
3.03 )
CALIFORNIA. REDWOOD
QO7 TnoTfitdire
22.0
75
0.66
1.53 )
QCT
28.0
75
0.70
1.43 )
R°?
22.0
75
0.70
1.43 )
807
28.0
75
0.75
1.33 )
16or
22.0
75
0.74
1.35 )
Ifi^jj
28.0
75
0.80
1.25 4)
CYPRXSB
28.7
86
0.67
1.49 1)
DoijoffAs FIR
0% moisture „ . , ... „
26.0
75
0.61
1.64 4)
34.0
75
CT.67
1.49 4)
R<7
26.0
75
0.66
1.52 4)
fl^
34.0
75
0.75
1.33 4)
16% . ,1Lll „ t
26.0
75
0.76
1.32 4)
34.0
75
0.82
1.22 4)
EAHTWN Hmnx»Cif
Cty Tnniftf.nre
22.0
75
0.60
1 67 4)
ftor
30.0
75
0.76
1.32 4)
R%
22.0
75
0.63
1.59 4)
9P7
30.0
75
0.81
1.23 4)
16%
22.0
75
0.67
1.49 (4)
30.0
75
0.85
1.18 (4)
HARD MAPLJC.. ... „
0*7 mofctrire
40.0
75
1.01
0.99 (4)
QOT
46.0
75
1.05
0 95 4)
W/
40.0
75
1.08
0.93 4)
s%
46.0
75
1.13
0.89 4)
16%
40.0
75
1.15
0.87 4)
Ifi%
46.0
75
1.21
0.83 4)
For notes see Page 97.
102
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND T ABIDES
TABLE 2.
CONDUCTIVITIES (k) AND CONDUCTANCES (O OF BUILDING
MATERIALS AND INSULATORS — Continued
The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness,
unless otherwise indicated.
Material
Description
DKNSITT
(La pin Cu FT)
MEAN TEMP.
(DEQ FAHR)
CONDUCTIVITT (k)
on
CONDUCTANCB (C)
-'•* ^'0
s &
j
WOODS— Continued
LONGLIBAF YELLOW Pirns
0% moisture __„„, Tir, r
30.0
7S !
0.76
1.32
f4)
40.0
75
0.86
1.16
(4)
R<y
30.0
75
0.83
1.21
(4)
gar
40.0
75 !
0.95
1.05
(4)
Ifi% ril ... , __.,.,
30.0
7S
0.89
1.12
(4)
16%
40.0
75
1.03
0.97
(4)
MAHQGANT
34.3
86
0.90
1.11
(1)
MjLPT.TH
44.3
86
1.10
0.91
(1)
\IAPLIB OB OAK_
1.15*
0.87
NORWAY PINE
0% moisture -
22.0
75
0.62
1.61
(4)
32.0
75
0.74
1.35
4)
oCff
22.0
75
0.68
1.47
4)
ty?
32.0
75
0.83
1.21
4)
16% ,, L
22.0
75
0.74
1.35
4)
16%
32.0
75
0.91
1.10
4)
TJ CfWXBS
0% moisture ... L
22.0
75
0.67
1.49
4)
32.0
75
0.79
1.27
4)
ow
22.0
75
0.71
1.41
4)
gar
32.0
75
0.84
1.19
4)
169r
22.0
75
0.74
1.35
4)
16%
32.0
75
0.90
1.11
4)
RED OAK
0% m^i"? ure
38.0
75
0.98
1.02
4)
48.0
75
1.18
0.85
4)
oar
38.0
75
1.03
0.97
4)
oft?
48.0
75
1.24
0,81
4)
16%
38.0
75
1.07
0.94
4)
16%
48,0
75
1.29
0.78
4)
SHQBTLHAi1 YBLLOW PINTS
26.0
75
0.74
1.35
4)
36.0
75
0.91
1.10
4)
oar
26.0
75
0.79
1.27
4)
Offi?
36.0
75
0.97
1.03
4)
16?^
26.0
75
0.84
1.19
4^
16%
36.0
75
1.04
0.96
4)
BofT KLM
28.0
75
0.73
1.37
4)
QOT
34.0
75
0.88
1.14
L)
gar
28.0
75
0.77
1.30
4)
8y
34.0
75
0.93
1.08
4)
169^
28.0
75
0,81
1.24
4
jgar
34.0
75
0.97
1.03
t
SOFT MAPLE-
0^ moisture
36.0
75
0.89
1.12
4)
09*
42.0
75
0.95
1.05
4)
8?^
36.0
75
0.96
1.04
4)
007
42.0
75
1.02
0.98
4)
16^
36.0
75
1.01
0.99
4)
16*7
42.0
75
1.09
0.92
4
SUGAR PTNIE
0% moiB ure ...L.,^ ,„ .r
22.0
75
0.54
1.85
4
28.0
75
0.64
1.56
4
8v
22.0
75
0.59
1.70
4}
oof
28.0
75
0.71
1.41
4}
169^
22.0
75
0.65
1.54
4)
167
28.0
75
0.78
1.28
4)
VIRGINIA. PINB
0
34.3
86
0.96
1.04
1)
WEST COAST BJBMLOCK.
0% moisture -..r.
22.0
75
0.68
1.47
4)
30.0
75
0.79
1.27
4)
Ott?
22.0
75
0.73
1.37
4}
am
30.0
75
0.85
1.18
4)
16v
22.0
75
0.78
1.28
4)
jg07
30.0
75
0.91
1.10
4)
WH « p___
31.2
86
0.78
1.28
1)
YELLOW PTKB
1.00
1.00
3)
0.80*
1.25
For notes see Page 97.
103
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 3. COEFFICIENTS OF TRANSMISSION (U) OF MASONRY WALLS*
Coefficients are expressed in Blu per hour per square foot per degree
Fahrenheit difference in temperature between the air on the two sides,
and are based on a wind Telocity of 15 mph.
}
THICKNESS
T
YP
ICAL
OF
WALL
CONSTRUCTION TYPE OF WALL
MASONRY
No.
(INCHES)
r<
=3*5
aa=
a
3t
P*
i
=S^
3
*>H
^>
&
Solid Brick
Based on 4-in. hard brick and the remainder
8
12
1
2
^a
te*=
•***
=2**
£
s
•**.
^2
3?
t
common brick.
16
3
t
•3^
g
./TU&C(
«ss*^±±S
)N
Hollow Tile
Stucco Exterior Finish.
The 8-in. and 10-in. tile figures are based on
8
4
1
^5
!S7
B
two cells in the direction of flow of heat. The
10
Q
12-in. tile is based on three cells in the direc-
12
6
y
g
tion of flow of heat. The 16-in. tile consists
16
7
1
I
1
r
^
of one 10-in. tile and one 6-in. tile each having
*4K
UL
•»,
**^
r
r
two cells in the direction of heat flow.
c
t
C!
— "^
5
9
8
8
N.
Jar:
— %<?
e^i
12
9
L
^
P
°T^
^J
Limestone or Sandstone
16
10
c
Sfe
"^».
a?
^jx
?
24
11
Concrete (Monolithic)
These figures may be used with sufficient
6
10
12
13
accuracy for concrete walls with stucco
16
14
"^ -N,
v."j£
• (
exterior finish.
20
15
9
0.
^ '
:
6
16
„•
0
Cinder (Monolithic)
Conductivity k ~> 4.36
10
16
17
18
y
9
:•'
~A
20
19
-••••.
••»•!.
•"
*f
6
20
••I^J^-
Haydite (Monolithic)
10
21
Conductivity k = 3.96
16
22
20
23
Cinder Blocks
8
24
Cores filled with dry cinders, 69.7 Ib per cu ft.
Cores filled with granulated cork, 5.12 Ib
8
25
per cu ft.
8
26
Cores filled with rock wool, 14.2 Ib per cu ft.
Based on one air cell in direction of heat flow.
Cores filled with granulated cork, 5.24 Ib per
8
12
27
28
4^>
*-^
\
cu ft.
Concrete Blocks
12
29
8
30
a»-
^
\
Cores filled with granulated cork, 5.14 Ib per
=35333
SSE
"•53S.
*
y
cuft.
8
31
****
"-^
C
/
Or
Based on one air cell in direction of heat flow.
12
32
•—•l^
Haydite Blocks
8
33
Cores filled with granulated cork, 5.06 Ib per
cuft.
8
34
Haydite Blocks
12
35
Cores filled with granulated corkr 5.6 Ib per
cu ft.
12
36
•Computed from factors marked by * in Table 2.
*Based on the actual thickness of 2-in. furring strips.
104
CHAPTER 5, HEAT TRANSMISSION COEFFICIENTS AND TABLES
INTERIOR FINISH
UNINSULATED WALLS
INSULATED WALLS
Plain walls — no in-
terior finish
g
S"
3
II
1
§1
5J2
'"'"'.3
§•*•»
O
!l!
S-P.S
Decorated building
board (M in.) with-
out plaster— furred
§"•$«
^
-S o
§£.
Si"!
g?3
3s|
lib
I1s5
si in*
-dlf^S
*l*89*3
j^y
Pi S-2«J2«\o"3
Plaster on metal
lath attached to fur-
ring strips (2 in.*)—
rock wool fill (155
in.&)«
gjp.si.1
52 till 1
llsSiJI
A
B
C
D
E
F
G
H
I
J
K
L
0.50
0.36
0.28-
0.46
0.34
0.27
0.30
0.24
0.20
0.32
0.25
0.21
0.30
0.24
0.20
0.23
0.19
0.17
0.22
0.19-
0-16-
0.16
0.14
0.13
0.14
0.12
0.11
0.23
0.19
0.17
0.12
0.11
0.10
0.20
0.17
0.15
0.40
0.39
0.30
0.25
0.38
0.37
0.29
0.24
0.26
0.26
0.22
0.19
0.28
9.27
0.22
0.19
0.26
0.26
0.22
0.19
0.20
0.20
0.17
0.16
0.20
0.19
0.17
0.15
0.15
0.15
0.14
0.12
0.13
0.13
0.12
0.11
0.20
0.20
0.18
0.16
0.11
0.11
0.10
0.097
0.18
0.18
0.16
0.14
0.71
0.58
0.49
0.37
0.64
0.53
0.45
0.35
0.37
0.33
0.30
0.25
0.39
0.34
0.31
0.26
0.37
0.33
0.30
0.25
0.26
0.24
0.22
0.20
0.25
0.23
0.22
0.19
0.18
0.17
0.16
0.15
0.15
0.14
0.14
0.13
0.26
0.24
0.22
0.20
0.13
0.13
0.12
0.11
0.23
0.21
0.20
0.18
0.79
0.62
0.48
0.41
0.70
0.57
0.44
0.39
0.39
0.34
0.29
0.27
0.42
0.37
0.31
0.28
0.39
0.34
0.29
0.27
0.27
0.25
0.22
0.21
0.26
0.24
0.21
0.20
0.19
0.18
0.16
0.15
0.16
0.15
0.14
0.13
0.27
0.25
0.22
0.21
0.13
0.13
0.12
0.12
0.23
0.22
0.20
0.18
0.46
0.33
0.22
0.19
0.43
0.31
0.22
0.18
0.29
0.23
0.17
0.15
0.30
0.24
0.18
0.15
0.29
0.23
0.17
0.15
0.22
0.18
0.15
0.13
0.21
0.18
0.14
0.13
0.16
0.14
0.12
0.11
0.14
0.12
0.10
0.09
0.22
0.18
0.15
0.13
0.12
0.11
0.09
0.09
0.19
0.16
0.13
0.12
0.44
0.30
0.21
0.17
0.41
0.29
0.20
0.17
0.28
0.22
0.16
0.14
0.29
0.23
0.17
0.14
0.28
0.22
0.16
0.14
0.21
0.17
0.14
0.12
0,21
0.17
0.14
0.12
0.16
0.14
0.11
0.10
0.13
0.12
0.10
0.09
0.21
0.18
0.14
0.12
0.12
0.10
0.09
0.08
0.19
0.16
0.13
0.11
0.42
0.31
0.39
0.29
0.27
0.23
0.28
0.23
0.27
0.22
0.21
0.18
0.20
0.17
0.16
0.14
0.13
0.12
0.21
0.18
0.12
0.11
0.19
0.16
0.22
0.23
0.37
0.21
0.22
0.35
0.17
0.19
0.25
0.18
0.18
0.26
0.17
0.18
0.25
0.14
0.15
0.19
0.14
0.14
0.19
0.12
0.12
0.15
0.11
0.10
0.13
0.14
0.15
0.19
0.09
0.09
0.11
0.13
0.14
0.17
0.20
0.19
0.17
0.16
0.16
0.13
0.13
0.11
0.10
0.14
0.09
0.13
0.56
0.52
0.32
0.34
0.32
0.24
0.23
0.17
0.14
0.24
0.12
0.21
0.41
0.49
0.39
0.46
0.27
0.30
0.28
0.32
0.27
0.30
0.21
0.23
0.20
0.22
0.15
0.16
0.13
0.14
0.21
0.23
0.12
0.12
0.18
0.20
0.36
0.34
0.26
0.26
0.24
0.19
0.19
0.15
0.13
0.19
0.11
0.17
0.18
0.17
0.15
0.15
0.14
0.13
0.12
0.10
0.09
0.13
0.08
0.12
0.34
0.32
0.25
0.25
0.24
0.19
0.18
0.14
0.12
0.19
0.11
0.17
0.15
0.14
0.13
0.13
0.12
0.11
0.11
0.09
0.08
0.11
0.08
0.10
eA waterproof membrane should be provided between the outer material and the insulation fill to
prevent possible wetting by absorption and a subsequent lowering of efficiency.
105
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 4. COEFFICIENTS OF TRANSMISSION (Z7) OF MASONRY WALLS
WITH VARIOUS TYPES OF VENEERS*
Coefficients are expressed in Blu per hour per square foot per degree
Fahrenheit difference in temperature between the air on the two sides,
and are based on a wind velocity of Iff mph.
TYPE OF WALL
TYPICAL
CONSTRUCTION
BACKING
WALL
No.
6 in.
4 in. Brick Veneer*
Hollow THe*
12 in.
4 in. Brick Veneer*
6 in.
10 in. Concrete
16 in.
8 in. Cinder Blocks
8 in. Cinder Blocks — Cores
filled with granulated cork,
5.12 Ib per cu ft.
12 in. Cinder Blocks
12 in. Cinder Blocks — Cores
filled with granulated cork,
5.24 Ib per cu ft.
4 in. Brick Veneer*
8 in. Concrete Blocks
8 in. Concrete Blocks — Cores
filled with granulated cork,
5.14 Ib per cu ft.
12 in. Concrete Blocks
8 in. Haydite Block
8 in. Haydite Block— Cores
filled with granulated cork,
5.06 Ib per cu ft.
12 in. Haydite Block
12 in. Haydite Block— Cores
filled with granulated cork,
5.6 per cu ft.
4 in. Cut-Stone Veneer*
Sin.
12 in. Common Brick
16 in.
6 in.
4 in. Cut-Stone Veneer1
Hollow me*
12 in.
4 in. Cut-Stone Veneer1
6 in.
10 in. Concrete
16 in.
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
puted from factors marked by * in Table 2.
d on the actual thickness of 2-in. furring strips.
<The 6-in., 8-in. and 10-in. tile figures are based on two cells in the direction of heat flow. The 12-in.
tHe is based on three cells in the direction of heat flow.
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
INTERIOR FINISH
UNINSULATED WALLS
INSULATE) WALLS
i
.5 S
§
3
3
If
g|
S3i
g-g
3
ii
PU 8
gg
li-p
ill
No plaster — deco-
rated rigid or build-
ing board interior
finish (ft in.)-
furred
§S
1
1
*§•« 1
|:§3
Plaster (J$ in.) on
cork board (1H in.)
setincementmortar
(H in.)
11 sill
Sj-slfll
§lt|
3i*Jk
aSif-*
j|jJ5g
slssa
Plaster (H in.) on
metal lath attached
to furring stripe
(2 in.*)— flexible in-
eulation (H in.) be-
tween furring strips
(one air space)
A
B
C
D
£
F
G
H
I
J
K
L
0.36
0.34
0.34
0.27
0.34
0.33
0.32
0.26
0.24
0.24
0.23
0.20
0.25
0.25
0.24
0.21
0.24
0.24
0.23
0.20
0.19
0.19
0.19
0.16
0.19
0.18
0.18
0.16
0.16
0.14
0.14
0.13
0.13
0.12
0.12
0.11
0.19
0.19
0.19
0.16
0.11
0.11
0.11
0.10
0.17
0.17
0.17
0.15
0.57
0.48
0.39
0.53
0.45
0.37
0.33
0.30
0.26
0.35
0.31
0.27
0.33
0.30
0.26
0.24
0.22
0.20
0.23
0.22
0.19
0.17
0.16
0.15
0.14
0.14
0.13
0.24
0.22
0.20
0.13
0.12
0 11
0.21
0.20
0.18
0.35
0.33
0.24
0.25
0.24
0.19
0.18
0.14
0.12
0.19
0.11
0.17
0.20
0.31
0.19
0.30
0.16
0.22
0.16
0.23
0.16
0.22
0.13
0.18
0.13
0.17
0.11
0.14
0.10
0.12
0.13
0.18
0.09
0.11
0.12
0.16
0.18
0.18
0.15
0.15
0.15
0.13
0.12
0.10
0.09
0.13
0.08
0.12
0.44
0.42
0.28
0.30
0.28
0.21
0.21
0.16
0.13
0.21
0.12
0.19
0.34
0.40
0.31
0.32
0.38
0.29
0.24
0.26
0.23
0.25
0.28
0.23
0.23
0.26
0.22
0.19
0.20
0.18
0.18
0.20
0.17
0.14
0.15
0.14
0.12
0.13
0.12
0.19
0.20
0.18
0.11
0.11
0.11
0.17
0.18
0.16
0.17
0.29
0.16
0.28
0.14
0.21
0,14
0.22
0.14
0.21
0.12
0.17
0.12
0.17
0.10
0.13
0.09
0.12
0.12
0.17
0.08
0.10
0.11
0.16
0.14
0.14
0.12
0.12
0.12
0.10
0.10
0.09
0.08
0.10
0.07
0.10
0.37
0.28
0.23
0.35
0.27
0.22
0.25
0.21
0.18
0.26
0.21
0.18
0.25
0.21
0.18
0.19
0.17
0.15
0.19
0.16
0.14
0.15
0.13
0.12
0.13
0.12
0.11
0.19
0.17
0.15
0.11
0.10
0.095
0.17
0.15
0.14
0.37
0.36
0.35
0.28
0.35
0.34
0.33
0.26
0.25
0.24
0.24
0.20
0.26
0.25
0.25
0.21
0.25
0.24
0.24
0.20
0.20
0.19
0.19
0.17
0.19
0.19
0.18
0.16
0.15
0.15
0.14
0.13
0.13
0.13
0.12
0.11
0.20
0.19
0.19
0.17
0.11
0.11
0.11
0.10
0.18
0.17
0.17
0.15
0.61
0.51
0.41
0.56
0.47
0.38
0.34
0.31
0.26
0.36
0.32
0.28
0.34
0.31
0.26
0.25
0.23
0.20
0.24
0.22
0.20
0.18
0.17
0.15
0.15
0.14
0.13
0.25
0.23
0.21
0.13
0.12
0.11
0.22
0.20
0.18
'Calculations include cement mortar (H in.) between veneer or facing and backing.
'Based on one air cell in direction of heat now.
/A waterproof membrane should be provided between the outer material and the insulation fill to
prevent possible wetting by absorption and a subsequent lowering of efficiency.
107
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 5. COEFFICIENTS OF TRANSMISSION (27) OF
VARIOUS TYPES OF FRAME CONSTRUCTION*
These coefficients ere expressed in Btu per hour per square foot per
degree Fahrenheit difference in temperature between the air on the two
sides, and are based on a wind velocity of 15 mph.
TYPICAL
CONSTRUCTION
i
'. EXTERIOR FINISH
i
TYPE OF SHEATHING
WALL
No.
rssT^fi
^
LJO^?;
^/Hfcvr
/WIVV J;
U*
/HtAT
"i ijr "^**
/HEAT
/WA
/Kt«
i
1
K" JM
MHG.
*80£
ttiHCi
•HWG
TtK<
P
KING
>UC1
1
rx
KIKS
«•,
1
1
J/.
r
\
1
\
c.\
>
Wood Siding or Clapboard
1 in. Wood*
65
2%2 in- Rigid Insulation
66
^ in. Plaster Board
67
Wood Shingles
1 in. Wood*
68
% in. Rigid Insulation*
69
% in. Plaster Board*
70
Stucco
1 in. Wood*
71
2%2 in. Rigid Insulation
72
M in. Plaster Board
73
Brick/ Veneer
1 in. Wood*
74
% in. Rigid Insulation
75
}i in. Plaster Board
76
"Computed from factors marked by * in Table 2.
plaste? board^0"**8 ^^ ^ be ^^ ^^ sufficient accuracy for plaster on wood lath or plaster on
•Based on the actual width of 2 by 4-in. studding, namely, 35i in.
108
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
INTERIOR FINISH
No INSULATION* BETWEEN STUDDING
INSULATION BETWEEN STUDDING
I
5
5
J3
3
i
5
J3
J
g
S
»
if
II
1
•a
«»
ll
&
Is
Plaster (^ in.) on rigid insulation
(H in.) on studding
i
~i
s!
0
|3
Plaster tt£ in.) on corkboard UH in.)
on studding
No piaster — decorated rigid or build-
ing board interior finish (J-a in.)
1 in. wood sheathing,1* furring strips,
plaster (H in.) on wood lath
!.-
ji
o o
3-!s
SJi
£ tt_g
Plaster (£4 m.) on metal lath* on
studding — flexible insulation (?£ in.)
between studding and in contact with
sheathing
§3
5| |
«*
B.ST
c^i
.111
gr*
*-.s|
ill
PH^aJS
Plaster (H in.) on metal lathh on
studding — flexible insulation (1 in.)
between studding — 2 air spaces
Plaster (£4 in.) on metal lathfc on
studding— rock wool fill (3fi« in.c)
between studding"*
A
B
c
D
E
F
G
H
I
J
K
L
M
0.25
0.26
0.25
0.19
0.15
0.11
0.19
0.17
0.20
0.17
0.15
0.12
0.072
0.23
0.24
0.23
0.18
0.14
0.11
0.18
0.14
0.19
0.17
0.13
0.10
0.070
0.31
0.33
0.31
0.22
0.17
0.13
0.23
• 0.19
0.24
0.20
0.17
0.13
0.076
0.25
0.26
0.25
0.19
0.15
0.11
0.19
0.17
0.20
0.17
0.15
0.12
0.072
0.19
0.20
0.19
0.15
0.12
0.10
0.16
0.14
0.16
0.14
0.11
0.094
0.066
0.24
0.25
0.24
0.19
0.15
0.11
0.19
0.19
0,19
0.17
0.15
0.12
0.071
0.30
0.31
0.30
0.22
0.16
0.12
0.22
0.19
0.23
0.20
0.17
0.13
0.076
0.27
0.29
0.27
0.20
0.16
0.12
0.21
0.15
0.22
0.19
0.14
0.11
0.074
0.40
0.43
0.40
0.26
0.19
0.14
0.28
0.22
0.29
0.24
0.20
0.14
0.081
0.27
0.28
0.27
0.20
0.15
0.12
0.21
0.17
0.21
0.18
0.16
0.12
0.074
0.25
0.26
0.25
0.19
0.15
0.11
0.19
OJL5
0.20
0.18
0.13
0.11
0.072
0.35
0.37
0.35
0.24
0.18
0.13
0.25
0.21
0.26
0.22
0.18
0.14
0.079
*Yellow pine or fir — actual thickness about % in.
•Furring strips between wood shingles and sheathing.
/Small air space and mortar between building paper and brick veneer neglected.
»A waterproof membrane should be provided between the outer material and the insulation fill to
prevent possible wetting by absorption and a subsequent lowering of efficiency.
AStud and rock wool fill areas combined.
109
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 6. COEFFICIENTS OF TRANSMISSION (U) OF FRAME INTERIOR WALLS
AND PARTITIONS**
Coefficients are expressed in Btu per hour per square foot per degree Fahrenheit difference in temperature
between the air on the two sides, and are based on still air (no wind) conditions on both sides.
TYPICAL CONSTRUCTION
WALL
No.
SINGLE
PARTITION
(FINISH
ON ONE
SIDE OF
STUDDING)
DOUBLE PARTITION
(FINISHED ON BOTH SIDES OP STUDDING)
Air
Space
Between
Studding
Flaked
Gffi*
Between
Studding
Rock
Wool
Fill*
Between
Studding
'Menble
Insulation
Between
Studding
(One Air
Space)
Stud Space Faced
One Side with
Bright Aluminum
Foil
TYPE OF WALL
A
B
C
D
E
F
Wood Lath and Plaster
On Studding
77
0.62
0.34
0.11
0.076
0.21
0.24
Metal Lath and Plaster*
On Studding
78
0.69
0.39
0,11
0.078
0.23
0.26
Plaster Board (% in.) and
Plaster* On Studding
79
0.61
0.34
0.10
0.075
0.21
0.24
M in. Rigid Insulation and
Plaster* On Studding
80
0.35
0.18
0.083
0.063
0.14
0.15
1 in. Rigid Insulation and
Plaster* On Studding
81
0.23
0.12
0.066
0.054
0.097
0.10
1H in. Corkboard and
Plaster* On Studding
82
0.16
0.081
0..052
0.044
0.070
0.073
2 in. Corkboard and
Plaster* On Studding
83
0.12
0.063
0.045
0.038
0.057
0.059
•Computed from factors marked by * in Table 2. 'Plaster on metal lath assumed %-in. thick.
*Thickness assumed 3^ inu 'Plaster assumed H-in- thick.
TABLE 7. COEFFICIENTS OF TRANSMISSION (27) OF MASONRY PARTITIONS^
Coefficients are expressed in Btu per hour per square foot per degree Fahrenheit difference in temperature
between the air on the two sides, and are based on still air (no wind) conditions on both sides.
TYPICAL CONSTRUCTION
W*S^^^
r
WALLS
WALLS
I
No.
PLAIN WALLS
(No PLASTER)
PLASTERED
ON ONE SIDE
PLASTERED
ON BOTH SIDES
TYPE OF WALL
A
B
C
4-in. Hollow Clay Tile
4-in. Common Brick
84
85
0.45
0.50
0.42
0.46
0.40
0.43
4-in. Hollow Gypsum Tile
86
0.30
0.28
0.27
2-in. Solid Plaster
87
0.53
•Computed from factors marked by * in Table 2.
110
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
a) o
g a
«
U .v.
§•3
^
U, |
I Is
G sh
P rj
««
S^
% B
per
are
NTS
per hour
and
8. COEFF
e expressed in
I
(%
s
2i§j5
§
H
s
.2
1
factors marked
ed to be % in.
ed to be % in.
21!
|i!
8
'55
u, d fl
.3 cs o
»1
111
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
« 3
8: 1
fc
o
li1
IP
4§5i
5lii-i
~a3ai
oooo oooo
"Iff
ml
gg§ .S(
ill gllc!
^^^ s
!|
!4E
I
ooaoooo
ClP-lpHrH
3
B
i
^«8
fea
|?
1§
g.S
&^
# CO CO CO
3
•3
I
S S
| f
I I
11
s§
03
l§
I
11
33
^s
H w 3 » a
!*!!
112
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
to "5
g 1-J
O — ;j
o i!
(3
stl
i!
§ -S
o 1
1-1 o
w
j
PQ
If
^1'^
:^|p
=1
•Cffl
§2
O CO iH 1H
rl r-t T-< tH
0 0 0 0
0 O 0 0
^j w g g
o* o" o o
0000
0000
3 3 T)
s a a
)H M 0
B a .2 .3
*!
il
l
•s
I 11
a si
32
§ ,44 .*< . « **
JMIfl
I***}?
puted
med
med
med 1
figures
rete.
113
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 11. COEFFICIENTS OF TRANSMISSION (U) OF VARIOUS TYPES
OF FLAT ROOFS COVERED WITH BUILT-UP ROOFING*
TYPICAL CONSTRUCTION
WITHOUT CEILINGS
WITH METAL LATH
AND
PLASTER CEILINGS*
TYPE OF ROOF DECK
THICKNESS
OF
ROOF
DECK
(INCHES)
No.
Precast Cement Tile
Concrete
Concrete
Concrete
m
Wood
Wood
Wood
Wood
1*
&
4»
Gypsum Fiber Concrete0
(2 in.) on Plaster Board
(Mm.)
Gypsum Fiber Concrete*
(3 in.) on Plaster Board
Gypsum Fiber Concrete*
(2 in.) on Rigid Insula-
lation Board (H in.)
Gypsum Fiber Concrete*
(2 in.) on Rigid Insula-
tion Board (1 in.)
10
12
Flat Metal Roofs
Coefficient of transmis-
sion of bare corrugated
iron (no roofing) is 1.50
Btu per hour per square
foot of projected area per
degree Fahrenheit dif-
ference in temperature,
based on an outside wind
velocity of 15 mph.
13
•Computed from factors marked by * in Table 2.
^Nominal thicknesses specified — actual thicknesses used in calculations.
•Gypsum fiber concrete- -87}$ per cent gypsum, 12H per cent wood fiber.
114
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
Coefficients are expressed in Btu per hour per square foot per degree
Fahrenheit difference in temperature between the air on the two sides,
and are based on an outside wind velocity of 15 mph.
WITHOUT CEILING— UNDER SIDE OF
ROOF EXPOSED
WITH METAL LATH AND
PLASTER CEILINGS*
No Insulation
I
3
2
3
2
.2
c*>
1
I
3
5
.?
EJ
es
3
1
CM
|
1
i
a
}
|
S
.5
^
j
1
1
1
1
0
A
B
c
D
E
F
G
H
I
j
K
L
M
N
0
P
0.84
0.37
0.24
0.18
0.14
0.22
0.16
0.13
0.43
0.26
0.19
0.15
0.12
0.18
0.14
0.11
0.82
0.72
0.64
0.37
0.34
0.33
0.24
0.23
0.22
0.17
0.17
0.16
0.14
0.13
0.13
0.22
0.21
0.21
0.16
0.16
0.15
0.13
0.12
0.12
0.42
0.40
0.37
0.26
0.25
0.24
0.1Q
0.18
0.18
0.15
0.14
0.14
0.12
0.12
0.11
0.18
0.17
0.17
0.14
0.13
0.13
0.11
0.11
0.11
0.49
0.37
032
0.23
0.28
0.24
0.22
0.17
0.20
0.18
0.16
0.14
0.15
0.14
0.13
0.11
0.12
0.11
0.11
0.096
0.19
0.17
0.16
0.13
0.14
0.13
0.12
0.11
0.12
0.11
0.10
0.091
0.32
0.26
0.24
0.18
0.21
0.19
0.17
0.14
0.16
0.15
0.14
0.12
0.13
0.12
0.11
0.10
0.11
0.10
0.097
0.087
0.15
0.14
0.13
0.11
0.12
0.11
0.11
0.096
0.10
0.095
0.092
0.082
0.40
0.32
0.26
0.19
0.25
0.22
0.19
0.15
0.18
0.16.
0.15
0.12
0.14
0.13
0.12
0.10
0.12
0.11
0.10
0.09
0.17
0.15
0.14
0.12
0.13
0.12
0.11
0.10
0.11
0.10
0.10
0.08
0.27
0.23
0.20
0.16
0.19
0.17
0.16
0.13
0.15
0.14
0.13
0.11
0.12
0.11
0.11
0.09
0.10
0.097
0.09
0.08
0.14
0.13
0.12
0.10
0.12
0.11
0.10
0.09
0.097
0.091
0.087
0.077
0.95
0.39
0.25
0.18
0.14
0.23
0.17
0.13
0.46
0.27
0.19
0.15
0.12
0.18
0.14
0.11
dThese coefficients may be used with sufficient accuracy for wood lath and plaster, or plaster board and
plaster ceilings. It is assumed that there is an air space between the under side of the roof deck and the
upper side of the ceiling.
115
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
£ Ii
§ •!'
5 28
O 3fB
1
If
.11
il
»-t o>o
y Is
3 f1
a i
| |
^ "i
pn* (-ui z) pjsoqaijoo
(til
P»JH
J^SBU pn* qjiq poo^
(•m^pjeoajajreij
j^sBUptre^Bn^api
ilslgii
I I,
o I o o o
B « -
; o o
F RO
AND
PICAL
RUCTION
CO
%
^
!
- i
»i
i «
llii
| sis
•s -a a c
s fi*
s sss
" ^I-s -
I 152 I
ci
^3*8
Hs
^ a«?
•3 §3! 3
^3-SI 2
an
-a aosts c^«5
laSI-Si'
S.9a-g«-! u
^•sj-s?
I-SgS^l
l^|3
a^olo^,
^issss
31-1 S"SCO ho14-1
l§1iiil
3|sf|w|
§
116
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
TABLE 13. COEFFICIENTS OF TRANSMISSION (£7) OF DOORS, WINDOWS, SKYLIGHTS
AND GLASS WALLS
Coefficients are based on a wind velocity of 15 mph, and are expressed in Biu per hour per square foot per
degree Fahrenheit difference in temperature between the air inside and outside of the door, window, skylight or watt
^ A . Windows and Skylights
DESCRIPTION ' L"
Single.-
Double--
Triple.-
0.45*
B. Solid Wood Doors*>,
NOMINAL
THICKNESS
INCHES
ACTUAL
THICKNESS U
INCHES
1
%
0.69
1/4
1K6 ; 0.59
1%
liKs
0.52
\%
IN
0.51
2
i«
0.46
2Ji
2N ; 0.38
3
25i
0.33
C. Glass Walls
DESCRIPTION
17
Hollow glass tile wall, 6 x 6 x 2 in. thick blocks
Wind velocity 15 mph, outside surface; still air, inside surface.-...
Still air, outside and inside surface.
0.60
0.48
«See Heating, Ventilating and Air Conditioning, by Harding and Willard, revised edition, 1932.
^Computed using C = 1.15 for wood; /i - 1.65 and/0 = 6.0.
"It is sufficiently accurate to use the same coefficient of transmission for doors containing thin wood
panels as that of single panes of glass, namely, 1.13 Btu per hour per square foot per degree difference
between inside and outside air temperatures.
it is probable that the values of U for these two types of roofs will
compare favorably.
The thicknesses upon which the coefficients in Tables 3 to 13, inclusive,
are based are as follows:
Brick veneer
Plaster and metal lath..
4 in.
Kin.
Plaster (on wood lath, plasterboard, rigid insulation, board
form, or corkboard)
Slate (roofing)
Stucco on wire mesh reinforcing
Tar and gravel or slag-surfaced built-up roofing.
1-in. lumber (S-2-S)
iH-in- lumber (S-2-S)
2-in. lumber (S-2-S) _„.
2j^-in. lumber (S-2-S)..
3-in. lumber (S-2-S).
4-in. lumber (S-2-S).,
Finish flooring (maple or oak)....,
Solid brick walls are based on 4-in. hard brick (high density) and the
remainder common brick (low density). Stucco is assumed to be 1-in.
thick on masonry walls. Where metal lath and plaster are specified, the
metal lath is neglected.
117
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
The coefficients of transmission of the pitched roofs in Table 12 apply
where the roof is over a heated attic or top floor so the heat passes directly
through the roof structure including whatever finish is applied to the
underside of the roof rafters.
Combined Coefficients of Transmission
If the attic is unheated, the roof structure and ceiling of the top floor
must both be taken into consideration, and the combined coefficient of
transmission determined. The formula for calculating the combined
coefficient of transmission of a top floor ceiling, unheated attic space, and
pitched roof, per square foot of ceiling area, is as follows:
UT X £/ce
U - „ , tfce (6)
Ur + ^r
where
U — combined coefficient to be used with ceiling area.
Ur = coefficient of transmission of the roof.
£/ce = coefficient of transmission of the ceiling.
n = the ratio of the area of the roof to the area of the ceiling.
Stating the formula in terms of the total heat resistance of the ceiling
and roof,
In selecting the values to be used for Ur and C/ce it should be noted
that the under surface of the roof and the upper surface of the ceiling are
more nearly equivalent to the boundary surfaces of an internal air space
than they are to the external surfaces of a wall. It would be more nearly
correct to use a value of 2.2 rather than the usual value of 1.65 as coef-
ficients for these surfaces. In most cases this would make only a minor
change in U. It should be noted that the over-all coefficient should be
multiplied by the ceiling and not the roof area.
If the unheated attic space between the roof and ceiling has no dormers,
windows or vertical wall spaces the combined coefficients may be used
for^determining the heat loss through the roof construction between the
attic and top floor ceiling. If the unheated attic contains windows and
vertical wall spaces these must be taken into consideration in calculating
the roof area and also its coefficient Z7r. In this case an approximate
value of Z7r may be obtained as the summation of the coefficient of each
individual section such as the roof, vertical walls or windows times its
percentage of total area. This coefficient may be used with reasonable
accuracy in the above formulae. If, however, there are roof ventilators
such that the attic air is substantially at outside temperature, then the
roof should be neglected and only the coefficient for the 'top floor ceiling
construction used.
Basements and Unheated Rooms
The heat loss through floors into basements and into unheated rooms
kept closed may be computed by assuming a temperature for these rooms
118
CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES
of 32 F. Additional information on the inside and outside temperatures
to be used in heat loss calculations is given in Chapter 7.
REFERENCES
Effects of Air Velocities on Surface Coefficients, by F. B. Rowley, A. B. Algren and
J. L. Blackshaw (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930} p. 123).
Wind Velocity Gradients Near a Surface and Their Effect on Film Conductance, by
F. C. Houghten and Paul McDermott (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 301).
Insulating Effect of Successive Air Spaces Bounded by Bright Metallic Surfaces, by
L. W. Schad (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 285).
Conductivity of Concrete, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E.
TRANSACTIONS, Vol. 38, 1932, p. 47).
Surface Coefficients as Affected by Direction of Wind, by F. B. Rowley and W. A.
Eckley (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 33).
Importance of Radiation in Heat Transfer Through Air Spaces, by E. R. Queer
(A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 77).
The Heat Conductivity of Wood at Climatic Temperature Differences, by F. B.
Rowley (A.S.H.V.E. TRANSACTIONS, Vol. 39, 1933, p. 329).
Insulating Value of Bright Metallic Surfaces, by F. B. Rowley (A.S.H.V.E. TRANS-
ACTIONS, Vol. 40, 1934, p. 413).
Thermal Properties of Concrete Construction, by F. B. Rowley, A. B. Algren and
Clifford Carlson (A.S.H.V.E. TRANSACTIONS, Vol. 42, 1936, p. 33).
Properties of Metal Foil as an Insulating Material, by J. L. Gregg (Refrigerating
Engineering, May, 1932).
Thermal Insulation with Aluminum Foil, by R. B. Mason (Industrial and Engineering
Chemistry, March, 1933).
Thermal Insulation of Buildings, Technical Paper No. 11 (American Architect,
May, 1934).
Thermal Properties of Concrete Construction, by F. B. Rowley, A. B. Algren and
Robert Lander (A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air Conditioning,
November, 1936, p. 621).
Radiation and Convection Across Air Spaces in Frame Construction, by G. B.
Wilkesand C. M. F. Peterson (A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air
Conditioning, August, 1937, p. 505).
Heat Insulation as Applied to Buildings and Structures, by E. A. Allcut, University
of Toronto, 1934.
House Insulation, Its Economies and Application, by Russell E. Backstrom (Report
of the National Committee on Wood Utilization, United States Government Printing
Office, 1931).
Heat Transmission Through Building Materials, by F. B. Rowley and A. B. Algren,
University of Minnesota Engineering Experiment Station Bulletin No. 8.
Calculation of Heat Transmission, by Margaret Fishenden and Owen A. Saunders.
Heating, Ventilating and Air Conditioning, by Harding and Willard, Revised Edition,
1932.
Heat Transmission, by W. H. McAdams.
Industrial Heat Transfer, by Shack.
PROBLEMS IN PRACTICE
1 • What is the coefficient U and how is it applied?
The coefficient U is the heat loss through walls, ceilings, and floors and the value depends
upon the construction and material, expressed in Btu per hour per square foot per degree
difference in temperature between the inside and outside. To determine the total heat
loss, multiply U for each material by the square feet of surface and the temperature
difference.
119
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
2 • Find the value of U for a 6-in. concrete wall with plaster on metal lath
attached to 2-in. furring strips with flanged J^-in. blanket insulation.
0.23 (Table 3, Wall 12L).
3 • A wall is built with two layers of J^-in. insulating material spaced 1 in.
apart; the air space is lined on one side with bright aluminum foil; mean
temperature is 40 F; still air on both sides of wall; k for insulating material
is 0.34. Calculate the value of U.
fl = 1.65; /0 = 1.65; a = 0.46
. l ft 397
"= 6'327
U - -J- - 0.158
4 • What is the inside surface temperature of a 6-in. solid concrete wall?
Inside ah*, 70 F; outside air, -20 F with 15 mph wind.
The temperature drop from point to point through a wall is directly proportional to the
heat resistance.
fl = 1.65; k for concrete = 12.62 ;/0 = 6.0
Over-all resistance R = + + JL .1
Temperature drop, inside air to surface — 1.65
Temperature drop, air to air 1.27
90
Temperature drop, inside air to surface = ., nfy „ , _g = 43
L.£( X l.oo
70 — 43 = 27 F, inside surface temperature of wall.
5 • How many inches of insulating material having a conductivity of 0.30
would be required, for the wall of Question 4, to raise the inside surface tem-
perature to 60 F?
Temperature drop, air to inside surface = 10 F; temperature drop, inside surface to out-
side air — 80 F. Therefore, the heat resistance from inside wall surface to outside air
must be eight times that from inside air to inside wall surface, or 8 X -rir- = 4.85. The
1.65
resistance for added material is, therefore,
485 - TO + = 4-19
4.19 X 0.30 - 1.25 in. of insulation.
6f, £-n unheated attic space in a residence has an equivalent pitched roof area
of 1560 sq ft and a ceiling area of 1200 sq ft. If 15 per cent of the roof area is
composed of vertical wall spaces having a value of U = 0.52, determine the
total heat loss per hour through the ceiling and roof for a temperature dif-
ference of 85 F, if U = 0.46 for the roof and U = 0.38 for the ceiling.
An approximate value of U for the roof is equivalent to the summation of coefficients
tor each individual section times its percentage of total area.
UT = (0.52 X 0.15) -f- (0.46 X 0.85) = 0.47.
Ratio of roof area, to ceiling = 1560 -f- 1200 = 1.3.
Substituting in Formula 6:
0.47 X 0.38
H = A U ft - /0) = 1200 X 0.235 X 85 = 23,900 Btu per hour.
120
Chapter 6
AIR LEAKAGE
Nature of Air Infiltration, Infiltration Through Walls, Window
Leakage, Door Leakage, Selection of Wind Velocity, Crack
Length used for Computations, Multi-Story Buildings, Heat
Equivalent of Air Infiltration
AIR leakage losses are those resulting from the displacement of heated
air in a building by unheated outside air, the interchange taking
place through various apertures in the building, such as cracks around
doors and windows, fireplaces and chimneys. This leakage of air must be
considered in heating and cooling calculations. (See Chapters 7 and 8.)
NATUBE OF Am INFILTRATION
The natural movement of air through building construction is due to
two causes. One is the pressure exerted by the wind; the other is the
difference in density of outside and inside air because of differences in
temperature.
The wind causes a pressure to be exerted on one or two sides of a
building. As a result, air comes into the building on the windward side
through cracks or porous construction, and a similar quantity of air
leaves on the leeward side through like openings. In general the resis-
tance to air movement is similar on the windward to that on the leeward
side. This causes a building up of pressure within the building and a
lesser air leakage than that experienced in single wa.ll tests as determined
in the laboratory. It is assumed that actual building leakages owing to
this building up of pressure will be 80 per cent of laboratory test values.
While there are cases where this is not true, tests in actual buildings
substantiate the factor for the general case. Tests on mechanically
ventilated classrooms of average construction have shown that air
infiltration acts quite independently of the planned air supply. Accor-
dingly, the heating or cooling load owing to air infiltration from natural
causes should be considered in addition to the ventilating load.
The air exchange owing to temperature difference, inside to outside, is
not appreciable in low buildings. In tall, single story buildings with
openings near the ground level and near the ceiling, this loss must be
considered. Also in multi-story buildings it is a large item unless the
sealing between various floors and rooms is quite perfect. This tempera-
ture effect is a chimney action, causing air to enter through openings at
lower levels and to leave at higher levels.
A complete study of all of the factors involved in air movement through
building constructions would be very complex* Some of the complicating
121
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
factors are: the variations in wind velocity and direction; the exposure of
the building with respect to air leakage openings and with ^ respect ^ to
adjoining buildings; the variations in outside temperatures asjnfluencing
the chimney effect; the relative area and resistance of openings on the
windward and leeward sides and on the lower floors and on the upper
floors; the influence of a planned air supply and the related outlet vents;
and the variation from the average of individual building units. A study
of infiltration points to the need for care in the obtaining of good building
construction, or unnecessarily large heat losses will result.
INFILTRATION THROUGH WALLS
Table 1 gives data on infiltration through brick and frame walls. The
brick walls listed in this table are walls which show poor workmanship
and which are constructed of porous brick and lime mortar. For good
workmanship, the leakage through hard brick walls with cement-lime
mortar does not exceed one-third the values given. These tests indicate
that plastering reduces the leakage by about 96 per cent; a heavy coat of
cold water paint, 50 per cent; and 3 coats of oil paint carefully applied,
28 per cent. The infiltration through walls ranges from 6 to 25 per cent
of that through windows and doors in a 10-story office building, with
imperfect sealing of plaster at the baseboards of the rooms. With perfect
sealing the range is from 0.5 to 2.7 per cent or a practically negligible
quantity, which indicates the importance of good workmanship in proper
sealing at the baseboard. It will be noted from Table 1, that the in-
filtration through properly plastered walls can be neglected.
The value of building paper when applied between sheathing and
shingles is indicated by Fig. 1, which represents the effect on outside
construction only, without lath and plaster. The effectiveness of plaster
properly applied is no justification for the use of low grade building paper
or of the poor construction of the wall containing it. Not only is it
TABLE 1. INFILTRATION THROUGH WALLS**
Expressed in cubic feet per square foot per hour
TTPB OF WALL
WIND VKLOCITT, MIUBS EBB HOUB
5
10
15
20
25
30
8Ji in. Brick TOL^gj-j-
1.75
0.017
4.20
0.037
7.85
0.066
12.2
0.107
18.6
0.161
22.9
0.236
i *> • T>— j-t» \\7 IT / i*ain. _„„„_.
1.44
0.005
3.92
0.013
7.48
0.025
11.6
0.043
16.3
0.067
21.2
0.097
13 in. Bnck Wall 1^^^^..
Frame Wall, with lath and plaster^
0.03
0.07
0.13
0.18
0.23
0.26
_ »The values given in this table are 20 per cent less than test values to allow for building up of pressure
in rooms and are based on test data reported in the papers listed at the end of this chapter.
BeVd *Ming P8intcd °f Cedar shingles' sheathi*g. building paper, wood lath and
122
CHAPTER 6. AIR LEAKAGE
0.45
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
INFILTRATION, C FH PER SQ FT OF WALL
FIG. 1. INFILTRATION THROUGH VARIOUS TYPES OF SHINGLE CONSTRUCTION
difficult to secure and maintain the full effectiveness of the plaster but
also it is highly desirable to have two points of high resistance to air flow
with an air space between them.
The amount of infiltration that may be expected through simple walls
used in farm and other shelter buildings, is shown in Fig. 2. The infil-
tration indicated in Figs. 1 and 2 is that determined in the laboratory and
should be multiplied by the factor 0.80 to give proper working values.
<r 0.40 - - -
g :::
140 160 180 200 220
INFILTRATION, C FH PER SQ FT OF WALL
FIG. 2. INFILTRATION THROUGH SINGLE SURFACE WALLS USED IN FARM AND
OTHER SHELTER BUILDINGS
123
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
WINDOW LEAKAGE
The amount of infiltration for various types of windows is given in
Table 2. The fit of double-hung wood windows is determined by crack
and clearance as illustrated in Fig. 3. The length of the perimeter opening
or crack for a double-hung window is equal to three times the width plus
two times the height, or in other words, it is the outer sash ^ perimeter
length plus the meeting rail length. Values of leakage shown in Table 2
for the average double-hung wood window were determined by setting
the average measured crack and clearance found in a field survey of a
large number of windows on nine windows tested in the laboratory. In
addition, the table gives figures for a poorly fitted window. All of the
figures for double-hung wood windows are for the unlocked condition.
Just how a window is closed, or fits when it is closed, has considerable
influence on the leakage. The leakage will be high if the sash are short,
if the meeting rail members are warped, or if the frame and sash are not
FIG. 3. DIAGRAM ILLUSTRATING CRACK AND CLEARANCE
fitted squarely to each other. It is possible to have a window with
approximately the average crack and clearance that will have a leakage
at least double that of the figures shown. Values for the average double-
hung wood window in Table 2 are considered to be easily obtainable
figures provided the workmanship on the window is good. Should it be
known that the windows under consideration are poorly fitted, the larger
leakage values should be used. Locking a window generally decreases its
leakage, but in some cases may push the meeting rail members apart and
increase the leakage. On windows with large clearances, locking will
usually reduce the leakage.
Wood casement windows may be assumed to have the same unit
leakage as for the average double-hung wood window when properly
fitted. ^ Locking, a normal operation in the closing of this type of window,
maintains the crack at a low value.
For metal pivoted sash, the length of crack is the total perimeter of the
movable or ventilating sections. Frame leakage on steel windows may be
neglected when they are properly grouted with cement mortar into brick
work or concrete. When they are not properly sealed, the linear feet of
sash section in contact with steel work at mullions should be figured at
25 per cent of the values for industrial pivoted windows as given in
Table 2.
124
CHAPTER 6. AIR LEAKAGE
H WINDOW. IN. OF WATER
D p H- j-
» 00 0 l\
{
y
-A/
-E
fl
/<
5U.U3
45.69
OZ
•=>
O
40.89g
CL
a
35,40s.
28.90 g
Q
$
20.42
0
1
I/
J
y
/
y
/
i
/
/
1
i
/
/ /
l\
y
/
/
\\
y
\\
/
f/
1
/
/
y
I
I
A
n
i
i
7
§
o. 04
\
1
/
A
B
C
D
-Without storm sash
-Storm sash, suspend
•Storm sash, fastened
With four turn button
-Same as C with wool
weatherstrip applied
to storm sash
ed
s
1
1
//
/
h
j
I
/
1
§
o
U4
*o->
7
f
I
/
V
)
VJ
/
X
i
o:
CL.
c
/
f
f
M
/
>
'l
50 100 150 200 250 300
INFILTRATION, CFH PER FOOT OF CRACK
FIG. 4. INFILTRATION THROUGH SASH PERIMETER OF WINDOW WITH AND WITHOUT
STORM SASH — J^-IN. CRACK AND J^-IN. CLEARANCE
Leakage values for storm sash are given in Figs. 4 and 5. When storm
sash are applied to well fitted windows, very little reduction in infiltration
is secured, but the application of the sash does give an air space which
reduces the heat transmission and helps prevent the frosting of the
windows. When storm sash are applied to poorly fitted windows, a
reduction in leakage of 50 per cent may be secured.
W, IN. OF WATER
:>»-•*-
DO K
\ If
y
{
^ WIND VELOCITY, MILES PER HOUR
1
y
-
7
li
/
M
/
/
/
^
/
(
/
)
/
z
*
f
/
s
]
s
jl
/
/
fl
^
PRESSURE DROP THROUG
£ g S
/
/
/
/
/
/
/
/
l\
\
/
*
A-Without storn
B- Storm sash, s
C- Storm sash, 1
with four tun
isash
uspend
^stened
i button
ed
s
/
/
/
/
/
s
^
^
+
-?
^
•*••
^
^
1
La
**
ts
E
&
0
!•
&
I
100 150 200 250 300 350 400 4
1NF1LTRATION.C F H PER FOOT OF CRACK
FIG. 5. INFILTRATION THROUGH SASH PERIMETER OF WINDOW WITH AND WITHOUT
STORM SASH— H-m. CRACK AND J^-IN. CLEARANCE
125
HEATING VENTIIIATING AIR CONDITIONING GUIDE 1938
TABLE 2, INFILTRATION THROUGH WINDOWS
Expressed in Cubic Feet per Foot of Crack per Hour&
Tr?« OF WINDOW
REMARKS
5
10
15
20
25
30
Double-Hung
Wood Sash
Windows
(Unlocked)
1 Around frame in masonry wall — not calkedb
3.3
8.2
14.0
20.2
27.2
34.6
Around frame In masonry wall — calkedb
0.5
1.5
2.6
3.8
4.8
5.8
Around frame in wood frame construction^
2.2
6.2
10.8
16.6
23.0
30.3
Total for average window, non-weather-
stripped, He-in. crack and ?&-in. clearancec.
Includes wood frame leakage^
6.6
21.4
39.3
59.3
80.0
103.7
Ditto, weatherstrippedd
4.3
15.5
23.6
35.5
48.6
63.4
Total for poorly fitted window, non- weather-
stripped, 5^-in. crack and ?£-m. clearance.*
Includes wood frame leakaged „
26.9
69.0
110.5
153.9
199.2
249.4
Ditto, weatlierstrippedd
5.9
18.9
34.1
51.4
70.5
91.5
Double-Hung
Metal
Windows*
Non-weatierstripped, locked
Non-weatherstripped, unlocked.
Weatherstripped, unlocked
20
20
6
45
47
19
70
74
32
96
104
46
125
137
60
154
170
76
Rolled
Section
Steel
Sash
Windows^
Industrial pivoteds, J4-in. crack.
Architectural projected, J^-in. crack**
Architectural projected, %-in. crackh .
52
15
20
6
14
3
8
108
36
52
18
32
10
24
176
62
88
33
52
18
38
244
86
116
47
76
26
54
304
112
152
60
100
36
72
372
139
182
74
128
48
92
Residential casement, l^-in. crack*
Residential casement, J^-in. crack*
Heavy casement section, projected, J^-in.
cracki .„ „
Heavy casement section, projected J^-in.
•eraeki
Hollow Metal, vertically pivoted windowf
30
88
145
186
221
242
WIND VELOCITY, MILES PIB HOUR
aThe values given In this table are 20 per cent less than test values to allow for building up of pressure in
rooms, and are based on test data reported in the papers listed at the end of this chapter.
f fcThe values given for frame leakage are per foot of sash perimeter as determined for double-hung wood
windows. Some of the frame leakage in masonry walls originates in the brick wall itself and cannot be
prevented by calking. For the additional reason that calking is not done perfectly and deteriorates with
tome, it is considered advisable to choose the masonry frame leakage values for calked frames as the average
determined by the calked and not-calked tests.
cThe fit of the average double-hung wood window was determined as }£-in. crack and ?&-in. clearance by
measurements on approximately 600 windows under heating season conditions.
dThe values given are the totals for the window opening per foot of sash perimeter and include frame
leakage and so-called elsewhere leakage. The frame leakage values included are for wood frame construction
but apply as well to masonry construction assuming a 50 per cent efficiency of frame calking.
•A %-in. crack and clearance represents a poorly fitted window, much poorer than average.
^Windows tested in place in building.
^Industrial pivoted, window generally used in industrial buildings. Ventilators horizontally pivoted
at center or slightly above, lower part swinging out.
_ ^Architectural projected made of same sections as industrial pivoted except that outside framing member
is heavier, and refinements in weathering and hardware. Used in semi-monumental buildings such as
schools. Ventilators swing in or out and are balanced on side arms. J^-in. crack is obtainable in the best
practice of manufacture and installation, Jfl-in. crack considered to represent average practice.
• Sf •** ^e ^esi«n and section shapes as so-called heavy section casement but of lighter weight. ki-£n. crack
practice* m P1"^^ <>f manufacture and installation, J^-in. crack considered to represent average
• u+ - - ^i "•— ££. se£tions- Ventilators swing in or out and stay set at any degree of opening. J^-in. crack
is obtainable m the best practice of manufacture and installation, fc-in. crack considered to represent
average practice.
With reasonable care in installation leakage at contacts where windows are attached to steel frame-
work and at muUions is negligible. With &-in. crack, representing poor installation, leakage at contact
Sndow? i^thfSbk18 * °ne"third' and at mullions about one-sixth of that given for industrial pivoted
126
CHAPTER 6. AIR LEAKAGE
DOO1 LEAKAGE
Doors vary greatly in fit because of their "large size and tendency to
warp. For a well fitted door, the leakage values for a poorly fitted double-
hung'wood window may be used. If poorly fitted, twice this figure should
be used. If weatherstripped, the values may be reduced one-half. A
single door which is frequently opened, such as might be found in a store,
should have a value applied which is three times that for a well fitted
door. This extra allowance is for opening and closing losses and is kept
from being greater by the fact that doors are not used as much in the
coldest and windiest weather.
The infiltration rate through swinging and revolving doors is generally
a matter of judgment by the engineer making cooling load determinations
and in the absence of adequate research data the values given in Table 3
represent current engineering practice. These values are based on the
average number of persons in a room at a specified time, which may also
be the same occupancy assumed for determining the outside ventilation
requirements outlined in Chapters 3 and 8.
TABLE 3. INFILTRATION THROUGH OUTSIDE DOORS FOR COOLING LOADS&
Expressed in Cubic Feet per Minute per Person in Room
APPLICATION
PA.IH 36 IN. SWINGING
DOOKS, SINGLE
ENTRANCEb
"D^r-ilr '
7.5
4.5
7.0
6.0
25.0
8.0
2.5
7.0
2.5
3.5
5.0
3.5
3.0
2.0
2.5
2.5
3.5
Tin? tvne.
Barber Shop
Drug Store -
Furrier
A/To.«'o QVirvn - •"
Men s onop
/"X-GC/N/i - -
Office Building
Public Building —
Restaurant -
Ql-n-id QfTvr*=- * * — —
aFor doors located m omy one wa.u <JL wiicxc v.^**, ^ — — - --------- - •„„:„„
Westibules with double pair swinging doors, infiltration may be assumed 75 per cent of swmgmg
on for 72 in. revolving doors may be assumed 60 per cent of swinging door values.
SELECTION OF WIND VELOCITY
Although all authorities do not agree upon the value of the wind veloc-
ity that should be chosen for any given locality, it is common engineering
practice to use the average wind velocity during the three coldest months
of the year. Until this point is definitely established the practice of
using average values will be followed. Average wind velocities for the
monlhs of December, January and February for various cities in the
United States and Canada are given in Table 2, Chapter /.
127
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
In considering both the transmission and infiltration losses, the more
exact procedure would be to select the outside temperature and the wind
velocity corresponding thereto, based on Weather Bureau records, which
would result in the maximum heat demand. Since the proportion of
transmission and infiltration losses varies with the construction and is
different for every building, the proper combination of temperature and
wind velocity to be selected would be different for every type of building,
even in the same locality. Furthermore, such a procedure would necessi-
tate a laborious cut-and-try process in every case in order to determine
the worst combination of conditions for the building under consideration.
It would also be necessary to consider heat lag due to heat capacity in the
case of heavy masonry walls, and other factors, to arrive at the most
accurate solution of the problem. Although heat capacity should be con-
sidered wherever possible, it is seldom possible to accurately determine the
worst combination of outside temperature and wind velocity for a given
building and locality. The usual procedure, as explained in Chapter 7,
is to select an outside temperature which is not more than 15 F above
the lowest recorded, and the average wind velocity during the months
of December, January and February.
The direction of prevailing winds may usually be included within an
angle of about 90 deg. The windows that are to be figured for prevailing
and non-prevailing winds will ordinarily each occupy about one-half the
perimeter of the structure, the proportion varying to a considerable extent
with the plan of the structure. (See discussion of wind movement in
Chapter 36.)
CRACK LENGTH USED FOR COMPUTATIONS
In no case should the amount of crack used for computation be less
than half of the total crack in the outside walls of the room. Thus, in a
room with one exposed wall, take all the crack; with two exposed walls,
take the wall having the most crack; and with three or four exposed walls,
take the wall having the most crack; but in no case take less than half the
total crack. For a building having no partitions, whatever wind enters
through the cracks on the windward side must leave through the cracks
on the leeward side. Therefore, take one-half the total crack for com-
puting each side and end of the building.
The amount of air leakage is sometimes roughly estimated by assuming
a certain number of air changes per hour for each room, the number of
changes assumed being dependent upon the type, use and location of the
room, as indicated in Table 4. This method may be used to advantage as
a check on the calculations made in the more exact manner.
MULTI-STORY BUILDINGS
In tall buildings, infiltration may be considerably influenced by tem-
perature difference or chimney effect which will operate to produce a
head that will add to the effect of the wind at lower levels and subtract
from it at higher levels. On the other hand, the wind velocity at lower
levels may be somewhat^ abated by surrounding obstructions. Further-
more,^ the chimney effect is reduced in multi-story buildings by the partial
isolation of floors preventing free upward movement, so that wind and
128
CHAPTER 6. AIR LEAKAGE
TABLE 4. AIR CHANGES TAKING PLACE UNDER AVERAGE CONDITIONS EXCLUSIVE
OF AIR PROVIDED FOR VENTILATION
KIND OP ROOM OB BUILDING
NUMBER or AIR CHANGM
TAKING PLACE
PER Horn
Rooms, 1 side exposed I 1
Rooms, 2 sides exposed i 1J
Rooms, 3 sides exposed 2
Rooms, 4 sides exposed 2
Rooms with no windows or outside doors._
Entrance Halls —
Reception Halls
2 to 3
2
Living Rooms.— ........................................................................... i 1 to 2
Dining Rooms ,
Bath Rooms
Drug Stores
Clothing Stores
Churches, Factories, Lofts, etc..
Ito2
2
2 to 3
1
temperature difference may seldom cooperate to the fullest extent.
Making the rough assumption that the neutral zone is located at mid-
height of a building, and that the temperature difference is 70 F, the
following formulae may be used to determine an equivalent wind velocity
to be used in connection with Tables 1 and 2 that will allow for both wind
velocity and temperature difference:
- 1.75 a (1)
+ 1.75 b (2)
where
Mt — equivalent wind velocity to be used in conjunction with Tables 1 and 2.
j|f = wind velocity upon which infiltration would be determined if tem-
perature difference were disregarded.
a = distance of windows under consideration from mid-height of building
if above mid-height.
b — distance if below mid-height.
The coefficient 1.75 allows for about one-half the temperature difference head.
For buildings of unusual height, Equation 1 would indicate negative
infiltration at the highest stories, which condition may, at times, actually
exist.
Sealing of Vertical Openings
In tall, multi-story buildings, every effort should be made to seal off
vertical openings such as stair-wells and elevator shafts from the re-
mainder of the building. Stair-wells should be equipped with self-closing
doors, and in exceptionally high buildings, should be closed off into
sections of not over 10 floors each. Plaster cracks should be filled.
Elevator enclosures should be tight and solid doors should be used.
If the sealing of the vertical openings is made effective, no allowance
need be made for the chimney effect. Instead, the greater^wind move-
ment at the high altitudes makes it advisable to install additional heating
surface on the upper floors above the level of neighboring buildings, this
additional surface being increased as the height is increased. One
129
HEATING VENTILATING Am CONDITIONING GUIDE 1938
arbitrary rule is to increase the heating surface on floors above neighboring
buildings by an amount ranging from 5 per cent to 20 per cent. This extra
heating surface is required only on the windward side and^on windy days,
and hence automatic temperature control is especially desirable with such
installations.
In stair- wells that are open through many floor levels although closed
off from the remainder of each floor by doors and partitions, the strati-
fication of air makes it advisable to increase the amount of heating surface
at the lower levels and to decrease the amount at higher levels even to the
point of omitting all heating surface on the top several floor levels. One
rule is to calculate the heating surface of the entire stair-well in the usual
way and to place 50 per cent of this in the bottom third, the normal
amount in the middle third and the balance in the top third.
HEAT EQUIVALENT OF AIR INFILTRATION
Sensible Heat Loss
The heat required to warm cold outside air, which enters a room by
infiltration, to the temperature of the room is given by the equation:
HB = 0.24 Q d (ti - t0) (3)
where
Hs = heat required to raise temperature of air leaking into building from t0 to t{
Btu per hour.
0.24 = specific heat of air.
Q = volume of outside air entering building, cubic feet per hour.
d = density of air at temperature t0, pounds per cubic foot.
t\ — room air temperature, degrees Fahrenheit.
t0 ~ outside air temperature, degrees Fahrenheit.
Latent Heat Loss
When it is intended to add moisture to air leaking into a room for the
maintenance of proper winter comfort conditions, it is necessary to
determine the heat equivalent to evaporate the required amount of water
vapor, which may be calculated by the equation :
7000
where
Hi = heat required to increase moisture content of air leaking into building from
Mo to Mi, Btu per hour.
Q — volume of outside air entering building, cubic feet per hour.
d = density of air at temperature ti, pounds per cubic foot.
Mi — vapor density of inside air, grains per pound of dry air.
Mo = vapor density of outside air, grains per pound of dry air.
L = latent heat of vapor at MI, Btu per pound.
It is sufficiently accurate to use d = 0.075 Ib, in which case equation 3
reduces to 5 and if the latent heat of vapor is assumed for general condi-
tions as 1060 Btu per pound equation 4 reduces to 6.
Hs = 0.018 Q (ti - to) (5)
fli = 0.0114 Q (Mi - Mo) (6)
While a heating reserve must be provided to warm inleaking air on
the windward side of a building, this does not necessarily mean that the
130
CHAPTER 6. AIR LEAKAGE
heating plant must be provided with a reserve capacity, since the inleaking
air, warmed at once by adequate heating surface in exposed rooms, will
move transversely and upwardly through the building, thus relieving
other radiators of a^part of their load. The actual loss of heat of a building
caused by infiltration is not to be confused with the necessity for pro-
viding additional heating capacity for a given space. Infiltration is a
disturbing factor in the heating of a building, and its maximum effect
(maximum in the sense of an average of wind velocity peaks during the
heating season above some reasonably chosen minimum)must be met
by a properly distributed reserve of heating capacity, which reserve, how-
ever, is not in use at all places at the same time, nor in any one place at
all times.
REFERENCES
Air Leakage, by F. C. Houghten and C. C. Schrader (A.S.H.V.E. TRANSACTIONS,
Vol. 30, 1924, p. 105).
Air Leakage around Window Openings, by C. C. Schrader (A.S.H.V.E. TRANSACTIONS,
Vol. 30, 1924, p. 313).
Neutral Zone in Ventilating, by J. E. Emswiler (A.S.H.V.E. TRANSACTIONS, Vol. 32,
1926, p. 59).
Infiltration through Plastered and Unplastered Brick Walls, by F. C. Houghten and
Margaret Ingels (A.S.H.V.E. TRANSACTIONS, Vol. 33, 1927, p. 377).
Effect of Frame Calking and Storm Sash on Infiltration around and through Windows,
by W. M. Richtmann and C. Braatz (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928T p. 547).
Air Leakage on Metal Windows in a Modern Office Building, by F. C. Houghten and
M. E. O'Connell (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928, p. 321).
The Weathertightness of Rolled Section Steel Windows, by J. E. Emswiler and
W. C. Randall (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928, p. 527).
Air Leakage through a Pivoted Metal Window, by F. C. Houghten and M. E.
O'Connell (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928, p. 519).
Air Infiltration through Various Types of Brick Wall Construction, by G. L. Larson,
D. W. Nelson and C. Braatz (A.S.H.V.E. TRANSACTIONS, Vol. 35, 1929, p. 183).
Pressure Differences across Windows in Relation to W:ind Velocity, by J. E. Emswiler
and W. C. Randall (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 83).
Air Infiltration Through Various Types of Wood Frame Construction, by G. L.
Larson, D. W. Nelson and C. Braatz (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 99).
Air Infiltration Through Double-Hung Wood Windows, by G. L. Larson, D. W.
Nelson and R. W. Kubasta (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 571).
Flue Action in Tall Buildings, by H. L. Alt (Heating, Piping and Air Conditioning,
May, 1932).
Air Infiltration Through Steel Framed Windows, by D. 0. Rusk, V. H. Cherry and
L. Boelter (Heating, Piping and Air Conditioning, October, 1932).
Investigation of Air Outlets in Class Room Ventilation, by G. L. Larson, D. W.
Nelson and R. W. Kubasta (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 463).
Influence of Stack Effect on the Heat Loss in Tall Buildings, by Axel Marin (A.S.H.
V.E. TRANSACTIONS, Vol. 40, 1934, p. 377).
Wind Velocities Near a Building and Their Effect on Heat Loss, by F. C. Houghten,
J. L. Blackshaw, and Carl Gutberlet (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 387).
Fuel Saving Resulting from the Use of Storm Windows and Doors, by A. P. Kratz and
S. Konzo (A.S.H.V.E. TRANSACTIONS, Vol. 42, 1936, p. 87).
The Infiltration Problem of Multiple Entrances, by A. M. Simpson and K. B. Atkinson
(A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air Conditioning, June, 1936).
Infiltration Characteristics of Entrance Doors, by A. M. Simpson (Refrigerating
Engineering, June, 1936).
Heating Requirements of an Office Building as Influenced by the Stack Effect, by
F. C. Houghten and Carl Gutberlet (A.S.H.V.E. JOURNAL SECTION, Heating, Piping
and Air Conditioning, July, 1937).
131
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
PROBLEMS IN PRACTICE
1 • What two natural forces cause infiltration?
c. Wind causes^ pressure to be exerted on one or two sides of a building with consequent
movement of air through openings.
i>. Temperature difference inside to outside causes a difference in density with con-
sequent entrance of air at lower openings and exit of air at higher openings.
2 • What is the neutral zone as applied to infiltration in buildings?
Due to temperature difference inside air tends to flow out of openings near the top of
the building and is replaced by outside air coming in at lower openings. At some height
no flow occurs in or out. This is referred to as the neutral zone and often is taken at the
mid-height of the building but may be higher or lower than this depending on several
factors.
3 • In what type of structure is infiltration due to temperature difference
of importance?
In tall open buildings, in multi-story buildings inadequately sealed between floors and
in stair- wells for multi-story buildings the temperature difference effect is important.
4 • What procedure is sometimes used to compensate for this temperature
or chimney effect in stair-wells?
One rulejs to place 50 percent of the calculated radiation in the bottom third, the normal
amount in the middle third and the remainder in the top third.
5 • Why is it customary to apply a correction factor to laboratory values before
calculating infiltration in buildings?
Most, if not all, laboratory values have been determined by exerting a certain wind
pressure across a single thickness of building construction. In actual building con-
struction the pressure drop due to wind velocity takes place in two steps, one through
the windward and the other through the leeward wall. Tests indicate that the leakage
in actual construction will be about 80 per cent of laboratory values and therefore this
factor has been applied in making up the tables in this chapter. The curves represent
laboratory data as taken with no correction applied.
6 • Is infiltration through walls of importance?
In the case of compound walls of good construction the heat loss due to infiltration is
usually negligibly low. In the case of single thickness walls without building paper
properly applied, the heat loss due to air leakage may be very high.
7 • How are the wind velocities and outside temperatures selected for infil-
tration calculations in heating?
It is common practice to take the average wind velocity for the three coldest months
and the temperature as 15 F above the coldest recorded by the Weather Bureau during
the proceeding 10 years.
80 Show the probable combined effects of infiltration due to temperature
difference and wind velocity on the ground floor and on the 15th floor of a 20-
story building 200 ft high with a 12 mph wind blowing.
At the ground floor the effective velocity is increased to:
Ke = V122 + 1.75 X 100 = 17.8 mph
At the 15th floor level it would be reduced to:
Me = V122 - 1.75 X 50 = 7.5 mph
9 • What is the value of storm sash in reducing infiltration?
The reduction depends on the relative fit of the window and the storm sash. Fig. 4
indicates for storm sash buttoned on a reduction at 20 mph from about 52 cfh per foot
of crack to 42 cfh. Fig. 5 indicates a reduction for a storm sash buttoned over a loosely
fitted window from 185 to 90 cfh.
132
Chapter 7
HEATING LOAD
Heat Demand Design Factors, Method of Procedure, Inside
and Outside Temperatures, Wind Velocity Effects, Auxiliary
Heat Sources, Wall Condensation, Heat Loss Computation
TO design any system of heating, the maximum probable heat^demand
must be accurately estimated in order that the apparatus installed
shall be capable of maintaining the desired temperature at all times. The
factors which govern this maximum heat demand — most of which are
seldom, if ever, in equilibrium — include the following:
1. Outside temperature. 1
2. Rain or snow. Outside Conditions
3. Sunshine or cloudiness. (The Weather)
4. Wind velocity. J
5. Heat transmission of exposed parts of building.
6. Infiltration of air through cracks, crevices and
open doors and windows.
7. Heat capacity of materials.
8. Rate of absorption of solar radiation by exposed
materials.
9. Inside temperatures.
10. Stratification of air.
11. Type of heating system.
12. Ventilation requirements.
13. Period and nature of^ occupancy.
14. Temperature regulation.
Building
Construction
Inside
Conditions
The inside conditions vary from time to time, the physical properties of
the building construction may change with age, and the outside conditions
are changing constantly. Just what the worst combination of all of these
variable factors is likely to be in any particular case is. therefore con-
iectural. Because of the nature of the problem, extreme precision in
estimating heat losses at any time, while desirable, is hard of attainment.
The procedure to be followed in determining the heat loss from any
building can be divided into seven consecutive steps, as follows:
1. Determine on the inside air temperature, at the breathing line or the i 30-in. line,
which is to be maintained in the building during the coldest weather. (See Table 1.) ^
2. Determine on an outside air temperature for design purposes, t^0 WfP1?1^;
temperatures recorded in the locality in question, which will provide for all but the
most severe weather conditions. Such conditions as may exist for only a few .consecu-
tive hours are readily taken care of by the heat capacity of the building itself.
(See Table 2.)
133
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
3. Select or compute the heat transmission coefficients for outside walls and glass;
also for inside walls, floors, or top-floor ceilings, if these are next to unheated space;
include roof if next to heated space. (See Chapter 5.)
4. Measure up net outside wall, glass and roof next to heated spaces, as well as any
cold walls, floors or ceilings next to unheated space. Such measurements are made from
building plans, or from tie actual building.
5. Compute the heat transmission losses for each kind of wall, glass, floor, ceiling
and roof in the building by multiplying the heat transmission coefficient in each case
by the area of the surface in square feet and the temperature difference between the
inside and outside air. (See Items 1 and 2.)
6. Select unit values and compute the heat equivalent of the infiltration of cold air
taking place around outside doors and windows. These unit values depend on the kind or
width of crack and wind velocity, and when multiplied by the length of crack and the
temperature difference between the inside and outside air, the result expresses the heat
required to warm up the cold air leaking into the building per hour. (See Chapter 6.)
7. The sum of the heat losses by transmission (Item 5) through the outside wall and
glass, as well as through any cold floors, ceilings or roof, plus the heat equivalent (Item 6)
of the cold air entering by infiltration represents the total heat loss equivalent for any
building.
Item 7 represents the heat losses after the building is heated and under
stable operating conditions in coldest weather. Additional heat is
required for raising the temperature of the air, the building materials and
the material contents of the building to the specified standard inside
temperature.
The rate at which this additional heat is required depends upon the
heat capacity of the structure and its material contents and upon the
time in which these are to be heated.
This additional heat may be figured and allowed for as conditions re-
TABLE 1. WINTER INSIDE DRY-BULB TEMPERATURES USUALLY SPECIFIED*
TTFB 07 BUILDING
DwjFAHR
TYPH OP BUILDING
DB&FAHE
SCHOOLS
Class rooms
70-72
THEATERS —
Seating space
68-72
Assembly rooms. ..
68-72
Lounge rooms.
68-72
Gymnasiums
55-65
Toilets
68
Toilets and baths
70
Wardrobe and locker rooms
Kitchens.- .„
65-68
66
HOTELS —
Bedrooms and baths
70
Dining and lunch rooms.
65-70
Dining rooms
70
Playrooms.
60-65
Kitchens and laundries
fifi
Natatoriums. . «
75
Ballrooms
65-68
HOSPITALS—
Private rooms.
70-72
Toilets and service rooms.
FTOMES
68
70-72
Private rooms (surgical)
70-80
STORES.-. _
65-68
Operating rooms . , .
70-95
PUBLIC BUILDINGS
68-72
Wards
68
WARM AIR BATHS
I2fi
Kitchens and laundries.
66
STEAM BATHS
110
Toiler
68
FACTORIES AND MACHINE SHOPS
fin ft*?
Bathrooms-.
70-80
H OUNDRIES AND BOILER SHOPS
Kfkftn
PAINT SHOPS...
80
**• ^S«m08tT?>mf<i?ablef <5r'bulb temperature to be maintained depends on the relative humidity and
£ Chapter 3 ^"^ " conaidered together constitute what is termed the effective temperature.
134
CHAPTER 7. HEATING LOAD
quire, but inasmuch as the heating system proportioned for taking care
of the heat losses will usually have, a capacity about 100 per cent greater
than that required for average winter weather, and inasmuch as most
buildings may either be continuously heated or have more time allowed
for heating-up during the few minimum temperature days, no allowance
is made except in the size of boilers or furnaces.
INSIDE TEMPERATURES
The inside air temperature which must be maintained within a building
and which should always be stated in the heating specifications is under-
stood to be the dry-bulb temperature at the breathing line, 5 ft above the
floor, or the 30-in. line, and not less than 3 ft from the outside* walls.
Inside air temperatures, usually specified, vary in accordance with the use
to which the building is to be put and Table 1 presents values which con-
form with good practice.
The proper dry-bulb temperature to be maintained depends upon the
relative humidity and air motion, as explained in Chapter 3. In other
words, a person may feel warm or cool at the same dry-bulb temperature,
depending on the relative humidity and air motion. The optimum winter
effective temperature for sedentary persons, as determined at the A.S.H.
V.E. Research Laboratory, is 66 deg.1
According to Fig. 6, Chapter 3, for so-called still air conditions, a
relative humidity of approximately 50 per cent is required to produce an
effective temperature of 66 deg when the dry-bulb temperature is 70 F.
However, even where provision is made for artificial humidification, the
relative humidity is seldom maintained higher than 40 per cent during the
extremely cold weather, and where no provision is made for humidifica-
tion, the relative humidity may be 20 per cent or less. Consequently, in
using the figures listed in Table 1, consideration should be given to
whether provision is to be made for humidification, and if so, the actual
relative humidity to be maintained.
Temperature at Proper Level: In making the actual heat-loss compu-
tations, however, for the various rooms in a building it is often necessary
to modify the temperatures given in Table 1 so that the air temperature
at the proper level will be used. By air temperature at the proper level is
meant, in the case of walls, the air temperature at the mean height be-
tween floor and ceiling; in the case of glass, the air temperature at the
mean height of the glass; in the case of roof or ceiling, the air temperature
at the mean height of the roof or ceiling above the floor of the heated
room ; and in the case of floors, the air temperature at the floor level. In
the case of heated spaces adjacent to unheated spaces, it will usually be
sufficient to assume the temperature in such spaces as the mean between
the temperature of the inside heated spaces and the outside air tempera-
ture, excepting where the combined heat transmission coefficient of the
roof and ceiling can be used, in which case the usual inside and outside
temperatures should be applied. (See discussion regarding the use of
combined coefficients of pitched roofs, unheated attics and top-floor
ceilings Chapter 5.)
*See Chapter 3, p. 63.
135
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
High Ceilings: Research data concerning stratification of air in build-
ings are lacking, but in general it may be said that where the increase in
temperature is due to the natural tendency of jthe warmer or less dense
air to rise, as where a direct radiation system is installed, the temperature
of the air at the ceiling increases with the ceiling height. The relation,
however, is not a straight-line function, as the amount of increase per foot
of height apparently decreases as the height of the ceiling increases, ac-
cording to present available information2.
Where ceiling heights are under 20 ft, it is common engineering practice
to consider that the Fahrenheit temperature increases 2 per cent for each
foot of height above the breathing line. This rule, sufficiently accurate
for most cases, will give the probable air temperature at any given level
for a room heated by direct radiation. Thus, the probable temperature
in a room at a point 3 ft above the breathing line, if the breathing line
temperature is 70 F, will be
(1.00 + 3 X .02) 70 = 74.2 F.
With certain types of heating and ventilating systems, which tend to
oppose the natural tendency of warm air to rise, the temperature differ-
ential between floor and ceiling can be greatly reduced. These include
unit heaters, fan-furnace heaters, and the various types of mechanical
ventilating systems. The amount of reduction is problematical in certain
instances, as it depends upon many factors such as location of heaters,
air temperature, and direction and velocity of air discharge. In some
cases it has been possible to reduce the temperature between the floor
and ceiling by a few degrees, whereas, in other cases, the temperature at
the ceiling has actually been increased because of improper design, instal-
lation or operation of equipment. So much depends upon the factors
enumerated that it is not advisable to allow less than 1 per cent per foot
(and usually more) above the breathing line in arriving at the air tem-
perature at any given level for any of these types of heating and ventilating
systems, unless the manufacturers are willing to guarantee that the par-
ticular type of equipment under consideration will maintain a smaller
temperature differential for the specific conditions involved.
Temperature at Floor Level: In determining mean air temperatures
just above floors which are next to ground or unheated spaces, a tempera-
ture 5 deg lower than the breathing-line temperature may be used, pro-
vided the breathing-line temperature is not less than 55 F.
OUTSIDE TEMPERATURES
The outside temperature used in computing the heat loss from a build-
ing is seldom taken as the lowest temperature ever recorded in a given
locality. Such temperatures are usually of short duration and are rarely
repeated in successive years. It is therefore evident that a temperature
somewhat higher than the lowest on record may be properly assumed in
making the heat-loss computations.
3Temperature Gradient Observations in a Large Heated Space, by G. L. Larson, D. W. Nelson and
O. C. Cromer (A.S.H.V.E. TRANSACTIONS, Vol. 39, 1933, p. 243).
Tests of Three Heating Systems in an Industrial Type of Building, by G. L. Larson, D. W. Nelson and
John James (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 185).
136
CHAPTER 7. HEATING LOAD
The outside temperature to be assumed in the design of any heating
system is ordinarily not more than 15 deg above the lowest recorded tem-
perature as reported by the Weather Bureau during the preceding 10
years for the locality in which the heating system is to be installed. In
the case of massive and^well insulated buildings in localities where the
minimum does not prevail for more than a few hours, or where the lowest
recorded temperature is extremely unusual, more than 15 deg above the
minimum may be allowed, due primarily to the fly-wheel effect of the heat
capacity of the structure. The outside temperature assumed and used in
the design should always be stated in the heating specifications. Table 2
lists the coldest dry-bulb temperatures ever recorded by the Weather
Bureau at the places listed.
If Weather Bureau reports are not available for the locality in question,
then the reports for the station nearest to this locality are to be used,
unless some other temperature is specifically stated in the specifications.
In computing the average heat transmission losses for the heating season
in the United States the average outside temperature from October 1
to May 1 should be used.
WIND VELOCITY EFFECTS
The effect of wind on the heating requirements, of any building should
be given consideration under two heads:
1. Wind movement increases the heat transmission of walls, glass, and roof, affecting
poor walls to a much greater extent than good walls.
2. Wind movement materially increases the infiltration (inleakage) of cold air through
the cracks around doors and windows, and even through the building materials them-
selves, if such materials are at all porous.
Theoretically as a basis for design, the most unfavorable combination
of temperature and wind velocity should be chosen. It is entirely possible
that a building might require more heat on a windy day with a moderately
low outside temperature than on a quiet day with a much lower outside
temperature. However, the combination of wind and temperature which
is the worst would differ with different buildings, because wind velocity
has a greater effect on buildings which have relatively high infiltration
losses. It would be possible to work out the heating load for a^ building
for several different combinations of temperature and wind velocity which
records show to have occurred and to select the worst combination; but
designers generally do not feel that such a degree of refinement is justified.
Therefore, pending further studies of actual buildings, it is recommended
that the average wind movement in any locality during December,
January and February be provided for in computing (1) the heat trans-
mission of a building, and (2) the heat required to take care of the infiltra-
tion of outside air.
The first condition is readily taken care of, as explained in Chapter 5,
by using a surface coefficient /0 for the outside wall surface which is based
on the proper wind velocity. In case specific data are lacking for any
given locality, it is sufficiently accurate to use an average wind velocity of
approximately 15 mph which is the velocity upon which the heat trans-
mission coefficient tables in Chapter 5 are based.
In a similar manner, the heat allowance for infiltration through cracks
137
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2. CLIMATIC CONDITIONS COMPILED FROM WEATHER BUREAU RECORDS**
COL. A
COL. B
COL.C
COL. D
COL. E
COL.F
State
City
Average
Temp.,
Oct. 1st-
May 1st
Lowest
Tempera-
ture
Ever
Reported
Average
Wind Vel-
ocity Dec.,
Jan., Feb.,
Miles per
Hour
Direction
of Prevail-
ing Wind,
Dec., Jan.,
Feb.
Ala..
Mobile
58.9
-1
10.4
N
Birmingham
53.8
-10
8.5
N
Ariz
Phoenix. —
59.5
12
6.4
E
Flagstaff.
35.8
-25
7.8
SW
Ark __
Fort Smith
50.4
-15
8.1
E
Little Rock
51.6
-12
8.7
NW
Calif
San Francisco
54.2
27
7.6
N
Los Angeles
58.5
28
6.3
NE
Colo
Denver
38.9
-29
7.5
S
Grand Junction
38.9
-21
5.3
NW
Conn.
New Haven
38.4
-15
9.7
N
D. C.
Washington
43.4
-15
7.1
NW
Fla
Jacksonville
62.0
10
9.2
NE
Ga
Atlanta
51.5
-8
12.1
NW
Savannah
58.5
8
9.5
NW
Idaho
Lewiston
42.3
-23
5.3
E
Pocatello
35.7
-28
9.6
SE
111
Chicago
36.4
-23
12.5
W
Springfield
39.8
-24
10.1
NW
Ind
Indianapolis.
Evansville
40.3
45.1
-25
-16
11.5
9.8
SW
S
Iowa
Dubuque...
33.9
-32
7.1
NW
Sioux City
32.6
-35'
11.6
NW
Kans
Concordia
39.8
-25
8.1
S
Ky.
Dodge City
Louisville
41.4
45.3
-26
-20
9.8
9.9
NW
SW
La
New Orleans
61.6
7
8.8
N
Shreveport
56.2
-5
8.9
SE
Me
Eastport.
31.5
-23
12.0
W
Portland
33.8
-21
9.2
NW
Md
Baltimore.
43.8
-7
7.8
NW
Mass.
Boston.
38.1
-18
11.2
W
Mich
Alpena
29.6
—28
12 4
W
Detroit
35.8
-24
12.7
SW
Marquette
28.3
-27
11.1
NW
Minn
Duluth
24 3
—41
12.6
SW
Minneapolis.
29.4
-33
n!s
NW
Miss
Vicksburg.
56.8
-1
8.3
SE
Mo
St. Joseph
St. Louis
40.7
43.6
-24
-22
9.3>
11.6
NW
S
Mont
Springfield
44.3
34.0
-29
-49
10.8
SE
W
Havre
27.6
-57
~o
SW
Nebr
Lincoln
37.0
-29
10.5
S
North Platte
35.4
-35
8.5
W
Nev „..
Tonopah.
39.4
-10
10.0
SE
Winnemucca
37.9
-28
8.7
NE
N. H. ..
Concord
33.3
-35
6.6
NW
N. T.
N.Y.::::::::::
Atlantic City
Albany
41.6
35.2
-9
-24
15.9
8.1
NW
S
Buffalo
34.8
-20
17.2
W
New York
40.7
-14
17.1
NW
^United States data from U. S. Weather Bureau.
Canadian data from Meteorological Service of Canada.
138
CHAPTER 7. HEATING LOAD
TABLE 2. CLIMATIC CONDITIONS COMPILED FROM WEATHER BUREAU RECORDS*
(Continued)
COL. A
COL.B
COL. C
COL. D
CouE
CoL,F
State
or
Province
City
Average
Temp.,
Oct. 1st-
May 1st
Lowest
Tempera-
ture Ever
Reported
Average
Wind Vel-
ocity Dec.,
Jan., Feb.,
Miles per
Hour
Direction
of Prevail-
ing Wind,
Dec., Jan.,
Feb.
N. M
N. C
N. Dak
Ohio
Santa Fe.
Raleigh.-.
Wilmington
Bismarck
Devils Lake
Cleveland
38.3
50.0
54.2
24.6
20.3
37 2
-13
-2
5
-45
-44
— 17
7.8
8.2
8.5
9.1
10.6
13 0
NE
SW
sw
NW
W
sw
Okla
Oreg
Pa
R I
Columbus
Oklahoma City
Baker
Portland
Philadelphia
Pittsburgh
Providence.
39.9
47.9
35.2
46.1
42.7
41.0
37.2
-20
-17
-24
-2
-6
-20
-17
12,0
12.0
6.9
7.5
11.0
11.7
12.8
sw
N
SE
S
NW
W
NW
s. c
Charleston
57.4
7
10.6
SW
S Dak.
Columbia
Huron
54.0
28.2
-2
-43
8.1
10.6
NE
NW
Tenn
Rapid City.
Knoxville
Memphis
33.4
47.9
51.1
-34
-16
-9
8.2
7.8
9.7
W
SW
s
Texas
Utah
El Paso
Fort Worth
San Antonio
Modena..
Salt Lake City
53.5
55.2
60.6
36.3
40.0
-5
-8
4
-24
-20
10.4
10.4
8.0
8.8
6.7
NW
NW
NE
W
SE
Vt
Va
Wash
W. Va.
Burlington
Norfolk.
Lynchburg.
Richmond
Seattle
Spokane
Elkins
31.5
49.3
46.8
47.0
44.8
37.7
39.4
-29
2
-7
-3
3
-30
-28
11.8
12.5
7.1
7.9
11.3
7.1
6.6
S
N
NW
SW
SE
SW
W
Wis
Parkersburg.™
Green Bay
42.6
30.0
-27
-36
7.5
10.4
SW
SW
Wyo.
Alta.
B. C
La Crosse~
Milwaukee..
Lander
Edmonton
Victoria
31.7
33.4
30.7
30.0
23.0
43.9
-43
-25
-41
-40
-57
- 1.5
7.3
11.5
6.0
5.0
6.5
12.5
s
W
NW
SW
sw
N
Man
N B
Vancouver
Winnipeg
Fredericton
42.0
17.5
27.0
2
-47
35
4.5
10.0
9.6
E
NW
NW
N. S
Ont.
Yarmouth
London
35.0
32.6
-12
-27
14.2
10.3
NW
SW
Ottawa
Port Arthur
Toronto
26.5
22.4
32.9
-34
-37
-26.5
8.4
7.8
13.0
NW
NW
SW
P. E. I
Que
Charlottetown
Montreal
29.0
27.8
-27
-29
9.4
14.3
sw
sw
Sask.._
Yukon
Quebec
Prince Albert
Dawson
24.2
15.8
2.1
-34
-70
-68
13.6
5.1
3.7
sw
W
s
^United States data from U. S. Weather Bureau.
Canadian data from Meteorological Service of Canada.
139
HEATING VENTIUITING AIR CONDITIONING GUIDE 1938
and walls (Tables 1 and 2, Chapter 6) must be based on the proper wind
velocity for a given locality. In the case of tall buildings special attention
must be given to infiltration factors. (See Chapter 6).
In the past many designers have used empirical exposure factors which
were arbitrarily chosen to increase the calculated heat loss on the side or
sides of the building exposed to the prevailing winds. It is also possible
to differentiate among the various exposures more accurately by calcu-
lating the infiltration and transmission losses separately for the different
sides of the building, using different assumed wind velocities. Recent
investigations show, however, that the wind direction indicated by
Weather Bureau instruments does not always correspond with the
direction of actual impact on the building walls, due to deflection by
surrounding buildings.
The exposure factor, which is still in use by many engineers, is usually
taken as 15 per cent, and is added to the calculated heat loss on the side or
sides exposed to what is considered the prevailing winter wind. There is a
need for actual test data on this point, and pending the time when it can
be secured, the question must be left to the judgment of the designing
engineer. It should be remembered that the values of U in the tables in
Chapter 5 are based on a wind velocity of 15 mph and that the infiltration
figures are supposed to be selected from the tables in Chapter 6 to cor-
respond to the wind velocities given in Table 2 of the present chapter.
The Heating, Piping and Air Conditioning Contractors National Associ-
ation has devised a method8 for calculating the square feet of equivalent
direct radiation required in a building. This method makes use of ex-
posure factors which vary according to the geographical location and the
angular situation of the construction in question in reference to pre-
vailing winds and the velocity of them.
AUXILIARY HEAT SOURCES
The heat supplied by persons, lights, motors and machinery should
always be ascertained in the case of theaters, assembly halls, and in-
dustrial plants, but allowances for such heat sources must be made only
after careful consideration of all local conditions. In many cases, these
heat sources should not be allowed to affect the size of the installation at
all, although they may have a marked effect on the operation and con-
trol of the system. In general, it is safe to say that where audiences are
involved, the heating installation must have sufficient capacity to bring
the building up to the stipulated inside temperature before the audience
arrives. In industrial plants, quite a different condition exists, and heat
sources, if they are always available during the period of human occu-
pancy, may be substituted for a portion of the heating installation. In
no case should the actual heating installation (exclusive of heat sources)
be reduced below that required to maintain at least 40 F in the building.
Electric Motors and Machinery
Motors and the machinery which they drive, if both are located in the
room, convert all of the electrical energy supplied into heat, which is
•See Standards of Heating, Piping and Air Conditioning Contractors National Association.
140
CHAPTER 7. HEATING LOAD
retained in the room if the product being manufactured is not removed
until its temperature is the same as the room temperature.
If power is transmitted to the machinery from the outside, then only
the heat equivalent of the brake horsepower supplied is used. In the
first case the Btu supplied per hour = Motor horsepower and
Efficiency of motor
in the second case Btu per hour = bhp X 2546, in which 2546 is the
Btu equivalent of 1 hp-hour. In high-powered mills this is the chief
source of heating and it is frequently sufficient to overheat the building
even in zero weather, thus requiring cooling by ventilation the year
round.
The heat (in Btu per hour) from electric lamps is obtained by multi-
plying the watts per lamp by the number of lamps and by 3.415. One
cubic foot of producer gas gives off about 150 Btu per hour; one cubic
foot of illuminating gas gives off about 535 Btu per hour; and one cubic
foot of natural gas gives off about 1000 Btu per hour. A Welsbach
burner averages 3 cu ft of gas per hour and a fish-tail burner, 5 cu ft
per hour. For information concerning the heat supplied by persons,
see Chapter 3.
In intermittently heated buildings, besides the capacity necessary
to care for the normal heat loss which may be calculated according to
customary rules, additional capacity should be provided to supply the
heat necessary to warm up the cold material of the interior walls, floors,
and furnishings. Tests have shown that when a cold building has had its
temperature raised to about 60 F from an initial condition of about 0 F,
the heat absorbed from the air by the material in the structure may vary
from 50 per cent to 150 per cent of the normal heat loss of the building.
It is therefore necessary, in order to heat up a cold building within a
reasonable length of time, to provide such additional capacity. If the
interior material is cold when people enter a building, the radiation of
heat from the occupants to the cold material will be greater than is
normal and discomfort will result. (See Chapter 3.)
WALL CONDENSATION
Condensation in the interior surfaces4 of buildings may cause irrep-
arable damage to manufactured articles and machinery. It often results
in short-circuiting of electric power, and causes disintegration of roof
structures not properly protected.
The prevalence of moisture on a surface is caused by the contact of
the warm humid air in a building with surfaces below the dew-point
temperature. It can be eliminated by (1) raising the surface temperature
with increased air velocities passing over the surface, or adding a sufficient
thickness of insulation, and (2) by lowering the humidity which is often
not possible due to manufacturing processes.
The condensation of moisture within walls5 is an important problem
with may types of construction under adverse conditions. The tempera-
*Preventing Condensation on Interior Building Surfaces, by Paul D. Close (A.S.H.V.E. TRANSACTIONS,
Vol. 36, 1930, p. 153).
"Condensation within Walls, by F. B. Rowley, A. B. Algren and C. E. Lund (A.S.H.V.E. JOURNAL
SECTION, Healing, Piping and Air Conditioning, January, 1938).
141
HEATING VENTIIATING AIR CONDITIONING GUIDE 1938
tures of the various parts of a wall are controlled by the type and amount
of insulation used and the vapor densities in the corresponding sections
are controlled by the type of vapor barriers installed. The transmission
of heat and vapor through a wall should be considered together, and in
most cases the proper combination of insulation and vapor barriers will
eliminate the possibilities of condensation within walls. A consideration
often overlooked in problems of condensation within walls is that a vapor
barrier should be placed on the warm side and not on the cold side of
a wall.
HEAT LOSS COMPUTATION EXAMPLE
Buift-up Cooftoq on 3* Coocr«Ve Hoof Deck
5fe U UnqAwfcnol Ax* MorHi * S
#e— 1
net 1 — IS Window* «od»
l.f r »de 4'JfUuLt.
fcron 1
nor i* 5*St&neConcra£e0n
faec-fn-p 3-Ond«rCooc«t«
j'£ OR Dirt -7
•outh
Lenqlb ttrf-0*
\
S
O
I
r
orCra
Solid V
&~
xxlDoow
-BP
5
FIG. 1. ELEVATION OF FACTORY BUILDING
Philadelphia, Pa.
-6F
..Northwest
60 F
1. LOCATION
2. LOWEST OUTSIDE TEMPERATURE. (Table 2)
3. BASE TEMPERATURE: In this example a design temperature 10 F above lowest
on record instead of 15 F is used. Hence the base temperature —
(- 6 + 10) = + 4 F.
4. DIRECTION OF PREVAILING WIND (during Dec., Jan., Feb.)
5. BREATHING-LINE TEMPERATURE (5 ft from floor)
6. INSIDE AIR TEMPERATURE AT ROOF:
The air temperature just below roof is higher than at the breathing line.
Height of roof is 16 ft, or it is 16 — 5 « 11 ft above breathing line. Allowing
2 per cent per foot above 5 ft, or 2 X 11 — 22 per cent, makes the tem-
perature of the air under the roof = 1,22 X 60 = 73.2 F.
7. INSIDE TEMPERATURE AT WALLS:
The air temperature at the mean height of the walls is greater than at
the breathing fine. The mean height of the walls is 8 ft and allowing 2 per
cent per foot above 5 ft, the average mean temperature of the walls is
1.06 X 60 = 63.6 F. By similar assumptions and calculations, the mean
temperature of the glass will be found to be 64.2 F and that of the doors
61.2 F.
8. AVERAGE WIND VELOCITY (Table 2)
9. OVER-ALL DIMENSIONS (See Fig. 1)...
10. CONSTRUCTION:
..11.0 mph
120 x 50 x 16 ft
Walls — 12-in. brick, with %-in. plaster applied directly to inside surface.
Roof — 3-in. stone concrete and built-up roofing.
142
CHAPTER 7. HEATING LOAD
Floor — 5-in. stone concrete on 3-in. cinder concrete on dirt.
Doors— One 12 ft x 12 ft wood door (2 in. thick) at each end.
Windows — Fifteen, 9 ft x 4 ft single glass double-hung windows on each side.
11. TRANSMISSION COEFFICIENTS:
Walls— (Table 3, Chapter 5, Wall 2B) U = 0.34
Roof— (Table 11, Chapter 5, Roofs 2A and 3A) U = 0.77
Floor— (Table 10, Chapter 5, Floors 5A and 6A) U = 0.63
Doors— -(Table 13B, Chapter 5) U = 0.46
Windows— (Table 13A, Chapters) U - 1.13
12. INFILTRATION COEFFICIENTS:
Windows— Average windows, non-weatherstripped, Ke-in- crack and
5^4-in. clearance. The leakage per foot of crack for an 11-mile wind
velocity is 25.0 cfh. (Determined by interpolation of Table 2,
Chapter 6.) The heat equivalent per hour per degree per foot of
crack is taken from Chapter 6.
25.0 X 0.018 = 0.45 Btu per deg Fahrenheit per foot of crack.
Doors — Assume infiltration loss through door crack twice that of windows
or 2 X 0.45 = 0.90 Btu per deg Fahrenheit per foot of crack.
Walls— As shown by Table 1, Chapter 6, a plastered wall allows so little
infiltration that in this problem it may be neglected.
13. CALCULATIONS: See calculation sheet, Table 3.
TABLE 3.
CALCULATION SHEET SHOWING METHOD OF ESTIMATING HEAT LOSSES OF
BUILDING SHOWN IN FIG. 1
PART OF BUILDING
WIDTH
IN
FEET
HEIGHT
IN
FEET
NET SUR-
FACE AREA
OR CRACK
LENGTH
COEFFI-
CIENT
TEMP.
DIFF.
TOTAL
BTU
North Wall:
Pn>k, M-1"^ piaster , .,
60
12
Ipair
16
12
doors
656
144
60
0.34
0.46
0.90
59.6
57.2
57.2
13,293
3,789
1,544*
Poors (2-ii?T wood) ,
Min- ^rac.k -. '
West Wall:
Ttriclc, J^-in . pfastfr
120
15x4
Double
Windov
16
9
Hung
re (15)
1380
540
450
0.34
1.13
0.45
59.6
60.2
60.2
27,964
36,734
6,095a
niass (Siiigte)L_
^ in Cr?»cV .... ~ , -
South Wall
Same as North Wall
18,626
TCaat Ws^l ,
Same as West Wall
70,793
Roof, 3-in. concrete and slag-
surfaced built-up roofing
50
120
6000
0.77
69.2
319,704
Floor, 5-in. stone concrete on
3-in. cinder concrete.^_..____
50
120
6000
0.63
5b
18,900
GRAND TOTAL of heat required for building in Btu pet
honr ,-,- L _^ 1L
517.442
aThis building has no partitions and whatever air enters through the cracks on the windward side must
leave through the cracks on the leeward side. Therefore, only one-half of the total crack will be used in
computing infiltration for each side and each end of building.
bA 5 F temperature differential is commonly assumed to exist between the air on one side of a large
floor laid on the ground and the ground.
143
HEATING VENTILATING Am CONDITIONING GUIDE 1938
PROBLEMS IN PRACTICE
1 • What is the relation between the sensible heat loss from a building and the
heat required for humidification?
A house with a volume of 14,000 cu ft has a heat loss 120 Mbh for standard uninsulated
frame construction and a 70 F temperature difference. Assuming a leakage rate of
1J^ air changes per hour it would require about 10 Mbh to maintain a relative humidity
of 45 per cent when the outside air is 0 F and 50 per cent relative humidity. By using
an insulation such as rock wool, the sensible heat loss of this house may be reduced to
approximately 77 Mbh. The insulation does not affect the humidification load, which
now assumes greater importance.
2 • What inside dry-bulb temperatures are usually assumed for: (a) homes,
(b) schools, (c) public buildings?
Referring to Table 1:
a. 70 to 72 F.
b. Temperature varies from 55 to 75 F, depending on the room. Classrooms, for instance,
are usually specified as 70 to 72 F.
c. 68 to 72 F.
3 • How is the outside temperature selected for use hi computing heat losses?
The outside temperature used in computing heat losses is generally taken from 10 to 15 F
higher than the lowest recorded temperature as reported by the Weather Bureau during
the preceding 10 years for the locality in which the heating system is to be installed.
In some cases where the lowest recorded temperature is extremely unusual, the design
temperature is taken even higher than 15 F above the lowest recorded temperature.
4 • What are the effects of wind movement on the heating load?
a. Wind movement increases the heat transmission of walls, glass, and roof; it affects
poor walls to a much greater extent than good walls.
b. Wind movement materially increases the infiltration (inleakage) of cold air through
the cracks around doors and windows, and even through the building materials them-
selves if such materials are at all porous.
5 • Calculate the heat given off by eighteen 200-watt lamps.
200 X 18 X 3.415 - 12,294 Btu per hour.
6 • A two-story, six-room, frame house, 28-ft by 30-ft foundation, has the
following proportions :
Area of outside walls, 1992 sq ft.
Area of glass, 333 sq ft.
Area of outside doors, 54 sq ft.
Cracks around windows, 440 ft.
Cracks around doors, 54 ft.
Area of second floor ceiling, 783 sq ft.
Volume, first and second floors, 13,010 cu ft.
Ceilings, 9 ft high.
The minimum temperature for the heating season is — 34 F, and the required
inside temperature at the 30-in. level is 70 F. The average number of degree
days for a heating season is 7851, and the average wind velocity is 10 mph,
northwest. *
The walls are constructed of 2-m. by 4-in. studs with wood sheathing, building
paper, and wood siding on the outside, and wood lath and plaster on the inside.
Windows are single glass, double-hung, wood, without weatherstrips. The
second floor ceiling is metal lath and plaster, without an attic floor. The roof
is of wood shingles on wood strips with rafters exposed. The area of the roof is
20 per cent greater than the area of the ceiling. Select values for the following :
(a) U for walls; (b) U for glass; (c) U for second floor ceiling; (d) U for roof;
144
CHAPTER 7. HEATING LOAD
(e) U for ceiling and roof combined; (f) air leakage, cubic feet per hour per foot
of window crack; (g) air leakage, cubic feet per hour per foot of door crack.
a. 0.25 (Table 5, Chapter 5).
b. 1.13 (Table 13, Chapter 5).
c. 0.69 (Table 8, Chapter 5).
d. 0.46 (Table 12, Chapter 5).
e. 0.31 (Equation 6, Chapter 5).
/. 21.4 (Table 2, Chapter 6).
g. 42.8, which is double the window leakage.
7 • Using the data of Question 6, calculate the maximum Btu loss per hour for
the various constructions, and show the percentage of the total heat which is
lost through each construction described.
Assume 2 per cent rise in temperature for each foot in height. The average temperature
will be 72.8 F for walls, doors, and windows, and 79.1 F for the second floor ceiling.
a. Outside walls
b. Glass
c. Doors
d. Second floor ceiling
e. Air leakage, windows
/. Air leakage, doors
Total
46,200 Btu loss
34,950 Btu loss
5,670 Btu loss
24,050 Btu loss
15,750 Btu loss
3,865 Btu loss
35.4 per cent of total
26.7 per cent of total
4.4 per cent of total
18.4 per cent of total
12.1 per cent of total
3.0 per cent of total
130,485 Btu loss 100.0 per cent of total
8 • For the house in Question 6, place 1-in. insulation in the outside walls and
second floor ceiling; k for insulation = 0.34. Use weatherstrip on doors and
windows, and double glass on the windows; G = 0.55. Calculate or select the
following values: (a) U for walls; (b) U for glass; (c) U for second floor ceiling;
(d) U for combination of ceiling and roof; (e) air leakage, cubic feet per hour
per foot of door crack; (f) air leakage, cubic feet per hour per foot of window
crack.
a. 0.144
b. 0.55
c. 0.23
d. 0.16
e. 15.5
/. 31.0
9 • Calculate the maximum Btu loss per hour and show the percentage loss by
each channel for the house as insulated in Question 8.
a. Outside walls
b. Glass
c. Doors
d. Ceiling
e. Air leakage, windows
/. Air leakage, doors
Total
26,650 Btu loss
17,000 Btu loss
5,670 Btu loss
12,420 Btu loss
11,400 Btu loss
2,795 Btu loss
35.1 per cent of total
22.4 per cent of total
7.4 per cent of total
16.4 per cent of total
15.1 per cent of total
3.6 per cent of total
75,935 Btu loss 100.0 per cent of total
10 • From the results of Questions 7 and 9, calculate the Btu saved and the
percentage saved by each change in construction.
UNINSULATED
INB^™
BTU SAVED
Fra CENT SATED
a. Outside walls
b. Glass
c. Doors
d. Ceiling
46,200
34,950
5,670
24,050
15,750
3,865
26,650
17,000
5,670
12,420
11,400
2,795
19,550
17,950
0
11,630
4,350
1,070
42.3
51.4
0
48.3
27.6
27.7
f. Air leakage, windows
/. Air leakage, doors.
145
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
11 • From the results of Questions 7 and 9, calculate the heat loads per heating
season in Btu and note the savings by better construction.
The 7851 degree days for the heating season multiplied by 24 hours, times the Btu loss
per hour for 1 F drop in temperature gives the Btu load per heating season.
Saving - 262,000,000 - 152,500,000 = 109,500,000 Btu.
12 • The dry-bulb temperature and the relative humidity at the ceiling of a
mixing room in a bakery are 80 F and 60 per cent, respectively. The roof is a
4-in. concrete deck covered with built-up roofing. If the lowest outside tem-
perature to be expected is — 10 F, what thickness of rigid fiber insulation will be
required to prevent condensation?
From Table 11, Chapter 5, U for the uninsulated roof = 0.72. From Table 2, Chapter 5,
k for rigid fiber insulation = 0.33. From the psychrometric chart the dew-point of air
at 80 F and 60 per cent relative humidity is 65 F. The ceiling temperature, therefore,
must not drop below 65 F if condensation is to be prevented.
When equilibrium is established, the amount of heat flowing through any component
part of a construction is the same for each square foot of area.
Therefore,
U [80 - (-10) ] = 1.65 (80 - 65)
where
U is the transmittance of the insulated roof.
Solving the equation, U = 0.275.
The resistance of the insulated roof = ~ 0_, = 3.64.
The resistance of the uninsulated roof = 77-^7 — 1.39.
U.7J
The resistance of the insulation = 3.64 — 1.39 = 2.25.
Resistance per inch of insulation = n Q0 = 3.0.
U.oo
Since a resistance of 2.25 is required, and 1 in. of insulation has a resistance of 3, one inch
will be sufficient to prevent condensation.
The same result might have been obtained by selecting an insulated 4-in. concrete slab
having a U of less than 0.275 from Table 11, Chapter 5. This 4-in. concrete slab with
1-in. rigid insulation has a U of 0.23 which is safe.
146
L
Chapter 8
COOLING LOAD
Conditions of Comfort, Design Outside Temperatures, Com-
ponents of Heat Gain, Normal Heat Transmission, Solar
Heat Transmission, Sun Effect Through Windows, Heat
Emission of Occupants, Heat Introduced by Outside Air, Heat
Emission of Appliances
OAD calculations for summer air conditioning are more complicated
, y than heating load calculations for the reason that there are several
more factors to be considered. Because of the variable nature of some of
the contributing load components and the fact that they do not neces-
sarily impose their maximum effect simultaneously, considerable care
must be exercised in determining their phase relationship in order that
equipment of proper capacity may be selected to maintain specified
indoor conditions.
CONDITIONS OF COMFORT
The conditions to be maintained in an enclosure are variable ^ and
depend upon several factors, especially the outside design conditions,
duration of occupancy and relationship between air motion, dry-bulb and
wet-bulb temperatures. Information concerning the proper effective
temperature to be maintained is given in Chapter 3, where are also tabu-
lated the most desirable indoor conditions to be maintained in summer for
exposures over 40 min (see Table 2, Chapter 3).
DESIGN OUTSIDE TEMPERATURES
Summer dry-bulb and wet-bulb temperatures of various cities are
given in Table 1. It will be noted that the temperatures are not the maxi-
mums but the design temperatures which should be used In air condition-
ing calculations. The maximum outside wet-bulb temperatures as given
in Weather Bureau reports usually occur only from 1 to 4 per cent of the
time, and they are therefore of such short duration that it is not practical
to design a cooling system covering this range. The temperatures shown
in Table 1 are in part based on available design conditions known ^to be
successfully applied and for those localities where this information is
lacking they are based on a study of the hourly temperatures in New York
City from which factors were derived and applied to the average maxi-
mum dry- and wet-bulb temperatures for other cities. This study covered
a twenty-year record of Weather Bureau temperatures. The design
147
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 1. DESIGN DRY- AND WET-BULB TEMPERATURES, WIND VELOCITIES, AND
WIND DIRECTIONS FOR JUNE, JULY, AUGUST, AND SEPTEMBER
STATE
CITY
DESIGN
DST-BULB
DESIGN
WET-BULB
SUMMER WIND
VELOCITY
MPH
PREVAILING
SUMMER WIND
DIRECTION
Ala
Birmingham
Mobile
95
95
78
80
5.2
8.6
S
sw
Ariz
Phoenix
105
76
6.0
w
Ark. . .
Little Rock
95
78
7.0
NE
Calif.
Los Angeles
90
70
6.0
SW
Colo.
San Francisco
Denver
90
95
65
64
11.0
6.8
sw
S
Conn
New Haven
95
75
7.3
S
Dela.
D. C.
Wilmington
Washington
95
95
78
78
9.7
6.2
sw
S
Fla.
Jacksonville,
95
78
8.7
sw
Tampa
94
79
7.0
E
Ga
Atlanta
95
75
7.3
NW
Idaho . ...
Savannah
Boise., _....
95
95
78
65
7.8
5.8
SW
NW
Ill
Ind _.
Iowa
Kansas
Ky.
Lav: ::
Maine.
Md
Mass.
Mich
Minn ~
Miss.
Mo
Mont_
Chicago _
Peoria
Indianapolis
Des Moines „
Wichita
Louisville
New Orleans
Portland-
Baltimore.-
Boston
Detroit
Minneapolis.-
Vicksburg
Kansas City.
St. Louis.
Helena
95
95
95
95
100
95
95
90
95
92
95
95
95
100
95
95
75
76
76
77
75
76
79
73
78
75
75
75
78
76
78
67
10.2
8.2
9.0
6.6
11.0
8.0
7.0
7.3
6.9
9.2
10.3
8.4
6.2
9.5
9.4
7.3
NE
S
SW
sw
S
sw
sw
S
sw
sw
sw
SE
sw
S
sw
sw
Nebr
Nev .
N. H.
N. J.
N. Y.
Lincoln
Reno
Manchester
Trenton
Albany
95
95
90
95
92
75
65
73
78
75
9.3
7.4
5.6
10.0
71
S
w
NW
sw
s
Buffalo
New York
93
95
75
75
12.2
12.9
sw.
sw
N. M..
Santa Fe
90
65
6 5
SE
N. C.
Asheville.
90
75
5.6
SE
N. Dak _
Ohio
Okla
Ores..
psZ :. ...
Wilmington
Bismarck
Cleveland
Cincinnati
Oklahoma City
Portland
Philadelphia-
95
95
95
95
101
90
95
79
73
75
78
76
65
78
7.8
8.8
9.9
6.6
10.1
6.6
97
SW
NW
S
sw
s
NW
SW
R. I „
S. C
S. Dak
Tenn.
Pittsburgh
Providence.
Charleston
Greenville.
Sioux Falls
Chattanooga
95
93
95
95
95
95
75
75
80
76
75
77
9.0
10.0
9.9
6.8
7.6
6 5
NW
NW
SW
NE
S
SW
Memphis
95
78
7.5
sw
148
CHAPTER 8. COOLING LOAD
TABLE 1. DESIGN DRY AND WET-BULB TEMPERATURES, WIND VELOCITIES, AND
WIND DIRECTIONS FOR JUNE, JULY, AUGUST, AND SEPTEMBER (Continued)
STATE
Crrr
DESIGN
DET-BCLB
SUMMER WIND i PBIVAUJNG
VELOCITY i SUMMER WIND
Mm
JLHRECriON
Texas
Dallas
100
78
9.4
s
Galveston.. _
95
SO
9.7
s
San Antonio
100
78
7.4
SE
Houston
95
78
7.7
S
El Paso,...
100
69
6.9
E
Utah
Salt Lake City
95
67
8.2
SE
Vt
Burlington
90
73
8.9
S
Va
Norfolk......
95
78
10.9
S
Richmond
95
78
6.2
SW
Wash.
Seattle.
85
65
7.9
S
Spokane ....
90
65
6.5
SW
W. Va
Parkersburg
• 95
75
5.3
SE
Wise.
Madison.
95
75
8.1
SW
Milwaukee.
95
75
10.4
s
Wyo. _
Cheyenne.
95
65
9.2
s
temperatures given are not exceeded more than 5 to 8 per cent of the time
during a cooling season of 1200 hours in June, July, August and September
for an average year.
COMPONENTS OF HEAT GAIN
A cooling load determination is composed of five components which
may be classified in the following manner:
1. Normal heat transfer through windows, walls, partitions, doors, floors, ceilings, etc.
2. Transfer of solar radiation through windows, walls, doors, skylights, or roof.
3. Heat emission of occupants within enclosures.
4. Heat introduced by infiltration of outside air or controlled ventilation.
5. Heat emission of mechanical, chemical, gas, steam, hot water and electrical
appliances^located within enclosures.
The components of heat gain, classified by source are further classified
as sensible and latent heat gain.
The first two components fall into the classification of sensible heat
gain, that is, they tend to raise the temperature of the air within the
structure. The last three components not only produce sensible heat
gain but they may also tend to increase the moisture content of the air
within the structure.
Normal Heat Transmission
By normal heat transmission, as distinguished from solar heat trans-
mission is meant the transmission of heat through windows, walls,
partitions, etc. from without to interior of enclosure by virtue of difference
between outside and inside air temperatures. This load is calculated in a
149
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
8
I
CO
8
nia
CHAPTER 8. COOLING LOAD
manner similar to that described in Chapter 7 (except that flow of heat
is reversed) by means of the formula:
Ht = AU(h-t) (1)
where
Ht = heat transmitted through the material of wall, glass, floor, etc., Btu per hour.
A — net inside area of wall, glass, floor, etc., square feet.
t = inside temperature, degrees Fahrenheit.
t0 = outside temperature, degrees Fahrenheit.
U = coefficient of transmission of wall, glass, floor, etc., Btu per hour per square foot
per degree Fahrenheit difference in temperature (Tables 3 to 13, Chapter 5),
Solar Heat Transmission
Calculations of the solar heatjtransmitted through walls and roofs
are difficult to determine because of periodical character of heat flow and
time lag due to heat capacity of construction.
The variation in solar intensity normal to sun in Btu per square foot
per hour on a horizontal surface, and on east, west, and south walls is
given in Fig. 1. The curves are drawn from A.S.H.V.E. Laboratory data
obtained by pyrheliometer, are based on sun time and apply for a per-
fectly clear day on August 1 at a north latitude of 40 deg. A study of
these curves discloses the periodic relationship and wide variation in
solar intensity on various surfaces. It will be observed that both the roof
and south wall radiation curves are in exact phase relationship with each
other and that whereas the east and west wall radiation curves overlap
those for roof and south wall, they do not overlap each other. This phase
relationship has an important bearing on the cooling load. Failure to
consider the periodical character of heat flow resulting from diurnal
movement of the sun and the lag due to heat capacity of the structure,
which determine the timing and magnitude of the heat wave flowing
through the wall, may result in a large error in load calculations.
The values of solar intensity appearing in Fig. 1 must not be confused
with the actual heat transmission through the wall for much of this heat
intensity on an outside surface is in part reflected and in part wiped off by
convection to the outside air. A mathematical solution for the deter-
mination of solar heat transmission has been developed but the equations
involved are too complex for practical application.1 From results of this
investigation and earlier studies,2 the Research Laboratory has prepared
Tables 2, 3, 4 and 5 which give the solar intensity (I) for various hours of
the day against walls of various orientations and horizontal surfaces and
the solar radiation ( JG ) transmitted through windows of various orien-
tations as well as skylights at various hours of the day. These values are
shown for north latitudes from 30 to 45 deg.
It should be noted that the values for (7) represent the rate of solar
intensity impinging against and not transmitted through walls and roofs
whereas values for (7G) represent actual rate of heat transmission through
windows and skylights. Since the amount of solar intensity actually
1Heat Transmission as Influenced by Heat Capacity and Solar Radiation, by F. C. Houghten, J. L.
Blackshaw, E. W. Pugh and Paul McDennott (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 231).
Absorption of Solar Radiation in its Relation to the Temperature, Color, Angle and Other Character-
istics of the Absorbing Surface, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E. TRANSACTIONS, Vol.
36, 1930, p. 137). - . _ . . .
151
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS,
AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS
FOR THE SAME ORIENTATIONS
For 30 Deg Latitude on the twenty-first of July, in Btu per sqft per hour
SUN
NORTHEAST EAST SOUTHEAST SOUTH SOUTHWEST i WIST
NORTHWEST
HORIZONTAL
SURFACE
TnoB
I
IG , I
IG I
IG I ' 1G I I IG
4:59
0
0 0
0 0
0 ; '
!
0
0
5:00; 1
0.9 1
0.9 0.3
02 • ' ,
0.01
0.005
6:00 47
41 51
44 , 24
17 :
9
5
7:00
136
106 160
140 , 90
68 ' ;
68
47
8:00
151
122 205
177 136
105
147
116
9:00
127
91 189
156 , 140
104
8 1
214
182
10:00! 79
47 , 141
103 122
85
31 12
j
265
231
11:00 21
6 ' 78
45 85
52
45 21
296
261
12:00
• 36
15 50 24
36
15
305
269
1:00
45 21
85
52
78
45
21
6
296
261
2:00
31 12
122
85
141
103
79
47
265
231
3:001 ',
8 1
140
104
189
156
127
91
214
182
4:00
136
105
205
177
151
122
147
116
5:00
90
68
160
140
136
106
68
47
6:00j
24
17
51
44
47
41
9
5
7:00;
0.3
0.2
1
0.9
1
0.9
0.01
0.005
7:01
;
1
j o
0
0
0
0
0
0
0
TABLE 3. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS,
AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS
FOR THE SAME ORIENTATIONS
For 85 Deg Latitude on the twenty-first of July, in Btu per sqft per hour.
i
STO Nosn
TtMB!
HAST
&
5T
Soum
3EAST
Soi
JTH
SOTJTI
[WEST
Wi
car
NORTI
3WEST
HORE
SUR
jONTAL
PACT
I
IG
/
IG
I
IG
J
'o
" 7
IG
/
IG
7
IG
7
IG
4:461 0
0
0
0
0
0
0
0
5:od 9
8
9
8
3
2
0.01
0.007
6:00! 67
58
72
63
35
26
15
8
7:00 142
120
174
152
103
78
77
53
8:00! 150
120
209
181
145
114
151
120
9:00 118
10:00 60
83
32
191
143
157
104
154
139
118
101
26
55
8
27
214
264
181
230
11:00 2
0.1
75
43
103
67
72
41
291
256
12:00
55
28
78
46
55
28
300
265
l:oJ
72
41
103
67
75
43
2
0.1
291
256
2:00
55
27
139
101
143
104
60
32
264
230
3:00!
26
8
154
118
191
157
118
83
214
181
4:00|
145
114
209
181
150
120
151
120
5:00;
103
78
174
152
142
120
77
53
6:00!
35
26
72
63
67
58
15
8
7:00
3
2
9
8
9
8
0.01
0.007
7:14
0
0
0
0
0
0
0
0
152
CHAPTER 8. COOLING LOAD
TABLE 4. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS
AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS
FOR THE SAME ORIENTATIONS
For 40 Deg Latitude on the twenty-first of July, in Bin per sqft per hour.
SUN
TIME
NORTHEAST
EAST
SOUTHEAST SOUTH SOUTHWEST WEST ISORTI
, HORIZONTAL
IWEST i SURFACE
T
j.
G
/G , J
JG L
JG 7
7G l
'G
4:31 0
0
0
0 0 : 0 '
\ 0 0
5:00, 14
12
14
12
-
3 i ; ;
1 1
0.2
6:00
72
63
80
70
40 29
19 11
7:001 143
120
180
158
112
87
; 82
57
8:00 143
111
211
182
155
124
8
2
152
121
9:00
104
69
192
158
168
133
46
22
|
]
213
178
10:00
46
22
143
104
156
117
77
45
!
j
255
225
11:00
75
43
121
83
95
60
15 , 4
i
284
249
12:00
73
42
103
67
73 1 42
293
258
1:00
15
4
95
60
121
83
75
43
284
249
2:00
77
45
156
117
143
104
46
22
25S
225
3:00
46
22
168
133
192
158
104
69
213
178
4:00
8
2
155
124
211
182
143
111
152
121
5:00
112
87
180
158
143
120
82
57
6:00
i
40
29
80
70
72
63
19
11
7:00
5 3
14
12
14
12
1
0.2
7:29
0 0
0
0
0
o
0
0
1
TABLE 5. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS
AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS
FOR THE SAME ORIENTATIONS
For 45 Deg Latitude on the twenty-first of July, in Btu per sqft per hour.
SUN
TIME
NORTHEAST
EAST
SOUTHEAST
SOUTH
SOUTHWEST
WEST
NOETHWEST
HORIZONTAL
SUMACS
J
*G
J
*G
J
'G
J
*G
7
'G
I
'G
I
*G
r
*G
4:26
0
0
0
0
0
0
0
0
5:00
25
22
24
21
9
6
2
07
6:00
89
77
99
88
52
39
26
15
7:00
149
125
194
170
125
99
90
63
8:00
140
109
219
189
171
139
22
8
156
123
9:00
92
58
194
160
183
148
65
36
210
177
10:00
33
13
144
106
171
134
98
63
251
217
11:00
75
43
139
101
121
83
32
13
274
240
12:00
91
67
128
90
91
67
282
247
1:00
32
13
121
83
139
101
75
43
274
240
2:00
98
63
171
134
144
106
33
13
251
217
3:00
65
36
183
148
194
160
92
58
210
177
4:00
22
8
171
139
219
189
140
109
156
123
5:00
125
99
194
170
144
125
90
63
6:00
52
39
99
88
89
77
26
15
7:00
9
6
24
21
25
22
2
0.7
153
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
transmitted through a surface depends upon the nature of the exterior
surface of wall or roof construction, it is necessary, in order to determine
actual amount of solar heat transmission, to apply correction factors to
the values of (I). Solar radiation factors and solar absorption coefficients
have been determined3 as indicated in Fig. 2 and Table 6 respectively.
0.20
0.18
0.14
U.Q.I:
I
SL.
-U
C0.08
0.06
0.04
0.02
0.1 O2 O3 O4 O5 O6 07
WALL TRANSMISSION COEFFICIENT, Uw
FIG. 2. SOLAR RADIATION FACTORS
.8
The solar heat conduction through a wall or roof exposed to the sun
may be expressed by the formula:
- A Fal
(2)
where
HR — Solar heat transmission, Btu per hour.
A - Area of wall or roof, square feet.
F = Percentage (expressed as a decimal) of the absorbed solar radiation which is
transmitted to the inside (Fig. 2) .
a = Percentage (expressed as a decimal) of the incident solar radiation which is
absorbed by the surface (Table 6).
/ - Actual intensity of solar radiation striking surface. Btu per hour per square
foot (Tables 2r 3, 4 and 5).
*A Rational Heat Gain Method for the Determination of Air Conditioning Cooling Loads, by F. H.
Faust, L. Levine and F. 0. Urban (A.S.H.V.E. TRANSACTIONS, Vol. 41. 1935? £ 327)7
154
CHAPTER 8. COOLING LOAD
The total amount of heat conducted through a wall exposed to the sun
is the sum of Ht and H& from Formulas 1 and 2.
The calculation of heat transmission through walls and roofs does not
take into consideration the heat capacity of the structure nor the con-
TABLE 6. SOLAR ABSORPTION COEFFICIENTS FOR DIFFERENT BUILDING MATERIALS
SURFACE MATERIAL
ABSORPTION COEFFICIENT
(a)
Very Light Colored Surfaces
White stone
Very light colored cement
White or light cream-colored paint
0.4
Medium Dark Surfaces
Asbestos shingles
Unpainted wood
Brown stone
Brick and red tile
Dark-colored cement
Stucco
Red, green or gray paint
0.7
Very Dark Colored Surfaces
Slate roofing
Tar roofing materials
Very dark paints
0.9
sequent time lag in the transmission of heat. In the case of massive walls
the time lag may amount to several hours4. Thus in many cases the wall
transmission cannot be added directly to the cooling load from dther
sources because the peak of the wall transmission load may not coincide
TABLE 7. TIME LAG IN TRANSMISSION OF SOLAR RADIATION THROUGH WALLS AND ROOFS
TYPE AND THICKNESS OF WAIJ. OB ROOF
Tom LAG,
HOTJHS
2-in. oine
\Yz
— i*i. ^.*^^- — -
o-in. concrete
3
4rin. gypsum
2^
3-in. concrete and 1-in. cork. . ~
2
2-in. iron and cork (equivalent to %-in. concrete and 2.15-in. cork)
4-in. iron and cork (equivalent to 5J^-in. concrete and 1.94-in. cork) . , .
2^
7H
8-in. iron and cork (equivalent to 16-in. concrete and 1.53-in. cork)
19
22-in. brick and tile wall
10
with the peak of the total cooling load and may even occur after the
cooling system has been shut down for the day. The data in Table 7 were
taken from A.S.H.V.E. research papers and whereas they result from a
study of experimental slabs, they give an approximate idea of the time lag
to be expected in various structures.
<Loc. Cit. Notes 1 and 2.
155
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Sun Effect Through Windows
Windows present a problem somewhat different from that of opaque
walls, because they permit a large percentage of the solar^ energy to pass
through undiminished ; only a small percentage (approximately 10 per
cent) is reflected. This fact permits the solar heat gain through windows
to be expressed by the simple formula:
where
(3)
HG = Solar radiation transmitted through a window, Btu per hour.
^G = Area of glass, square feet.
^G — Amount of solar radiation transmitted directly through the glass, Btu per hour
per square foot (Tables 2, 3, 4 and 5).
Values for solar heat transmission through glass as determined by
Formula 3 apply only to unshaded windows. Tests at the A.S.H.V.E.
Research Laboratory* have determined the percentages of heat from
solar radiation actually delivered to a room with bare windows and with
various types of outdoor and indoor shading. The data in Table 8 are
taken from these tests.
TABLE 8. SOLAR RADIATION TRANSMITTED THROUGH BARE AND SHADED WINDOWS
TTPB OF APPUBTENANCB
FINISH
FACING
SUN
PEB CENT
TO ROOM
Bare window glass.. ..
97
Canvas awniner .
Plain
28
Canvas awning
Aluminum
22
Inside shade, fully drawn
Aluminum
45
Inside shade, one-half drawn . .
Buff
68
Inside Venetian blind, fully covering window, slats at 45 deg
Outside Venetian blind, fully covering window, slats at 45 deg....
Aluminum
Aluminum
58
22
The percentage values in this table were obtained by dividing the total
amount of heat actually entering through the shaded window by the total
amount of heat calculated to enter through a bare window (solar radiation
plus glass transmission based on observed outside glass temperature).
For bare windows on which the sun shines, the transmission of heat from
outside air to glass is small or negative because the glass temperature is
raised by the solar radiation absorbed. Therefore, in calculating the
total heat gain through windows on the sunny sides of buildings, it is
sufficiently accurate to determine the total cooling load due to the win-
dow, as the solar radiation times the proper factor from Table 8 and to
neglect the heat transmission through the glass caused by the difference
between the temperatures of the inside and outside air.
Although Table 8 shows that 97 per cent of the heat from solar radia-
tion is delivered to a room through bare window glass, more recent tests6
*Radiation of Energy Through Glass, by J. L. Blackshaw and F. C. Houghten (A.S.H.V.E. TRANS-
ACTIONS, Vol. 40, 1934, p. 93). Studies of Solar Radiation Through Bare and Shaded Windows, by F. C.
Houghten, Carl Gutberlet, and J. L. Blackshaw (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 101).
•Cooling Requirements of Single Rooms in a Modern Office Building, by F. C. Houghten, Carl Gutberlet,
and Albert J. Wahl (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 53).
156
CHAPTER 8. COOLING LOAD
have indicated that in the case of a building having floors of high heat
capacity such as concrete floors on which the solar radiation falls, approxi-
mately one-half of the heat entering a bare window is absorbed by the
floor and does not immediately become a part of the cooling load but is
delivered back to the air in the building at a slow rate over a period of
24 hours or longer.
The maximum solar intensity on any surface is of limited duration as
shown in Fig. 1. In the case of windows the total energy impinging on the
glass before and after the time of maximum intensity is further reduced
by increased shading^ of the glass from the frame, or wall. The cooling
load due to solar radiation therefore does not have to be calculated as a
steady load. Another point which should be noted is that the maximum
solar radiation load on the east wall occurs early in the morning when the
outside temperature is low.
In a paper7 by the A.S.H.V.E. Research Laboratory it was shown that
ordinary double strength window glass transmits no measurable amount
of energy radiated from a source at 500 F or lower; that it transmits only
6.0 and 12.3 per cent of the total radiation from surfaces at 700 F and
1000 F, respectively; and that it transmits 65.7 per cent of the radiation
from an arc lamp, 76.3 per cent of the radiation from an incandescent
tungsten lamp, and 89.9 per cent of the radiation from the sun. Thus,
glass windows in a room constitute heat traps, which allow rather free
transmission of radiant energy into the room from the sun to warm objects
in it, but do not allow the transmission of re-radiated heat from these
same objects.
Tests have been made which indicated that sunshine through window
glass is the most important factor to contend with in the cooling of an
office building. At times it was shown to account for as much as 75 per
cent of the total cooling necessary. Because of the importance of the
sunshine load, cooling systems should be zoned so that the side of the
building on which the sun is shining can be controlled separately from the
other sides of the building. If buildings are provided with awnings so
that the window glass is shielded from sunshine, the amount of cooling
required will be reduced and there will also be less difference in the cooling
requirements of different sides of the building. The total cooling load
for a building exposed to the sun on more than one side is of course less
than the sum of the maximum cooling loads in the individual rooms since
the maximum solar radiation load on the different sides occurs at different
times. In determining the total cooling load for a building if the time
when the maximum load occurs is not obvious, the load should be calcu-
lated for various times of day to determine the times at which the sum
of the loads on the different sides of the building is a maximum.
Heat Emission of Occupants
The heat and moisture given off by human beings under various states
of activity are shown in Figs. 8 to 11 and Table 4 of Chapter 3. It will be
observed that the rate of sensible and latent heat emission by human
beings varies greatly depending upon state of activity. In many applica-
tions this component becomes a large percentage of total load.
Txx:. Cit. Note 5.
157
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Heat Introduced by Outside Air
An allowance must be made for the heat and moisture in the outside
air introduced for ventilation purposes or entering the building through
cracks, crevices, doors, and other places where infiltration might occur.
The volume of air entering due to infiltration may be estimated from
data given in Chapter 6. Information on the amount of outside air
required for ventilation will be found in Chapter 3 .
In the event the volume of air entering an enclosure due to infiltration
exceeds that required for ventilation, the former should be used as a basis
for determining the portion of the load contributed by outside air. Where
volume of air required for ventilation exceeds that due to infiltration it is
assumed that a slight positive pressure will exist within the enclosure with
a resulting exfiltration instead of infiltration. In this case the air required
for ventilation is used in determining outside air load.
The sensible heat gain resulting from the outside air introduced may be
determined by the following formula:
Hs = 0.24 X 60 do Q (to - 0 (4)
where
Hs — sensible heat to be removed from outside air entering the building, Btu per hour.
Q = volume of outside air entering building, cubic feet per minute.
do - density of air, pounds of dry air per cubic foot at temperature t0.
to = temperature of outside air, degrees Fahrenheit.
t = temperature of inside air, degrees Fahrenheit.
The total heat gain resulting from outside air introduced may be deter-
mined by the following formula:
H = 60 do Q (h0 - h) (5)
where
H — total heat to be removed from outside air entering the enclosure, Btu per hour.
Q = volume of outside air entering enclosure, cubic feet per minute.
do = density of air, pounds of dry air per cubic foot of air (at temperature /0).
fio = heat content of mixture of outside dry air and water vapor, Btu per pound of
dry air (at temperature t0).
h = heat content of mixture of inside dry air and water vapor, Btu per pound of
dry air (at temperature t).
The latent heat gain resulting from outside air introduced may be
determined by the following formula:
Hi = H - Hn (6)
where
Hi - latent heat to be removed, Btu per hour.
H — total heat to be removed, Btu per hour.
Hs = sensible heat to be removed, Btu per hour.
Heat Emission of Appliances
Heat generating appliances which give off either sensible heat or both
sensible and latent heat in an air conditioned enclosure may be divided
158
CHAPTER 8. COOLING LOAD
into three general classes of equipment or devices:
1. Electrical appliances.
2. Gas appliances.
3. Steam heating appliances.
In the first group may be found such devices as lights, motors, toasters,
waffle irons, etc. The capacities of most electrical devices may be
determined from the watt capacity indicated on their^ name plates.
The Btu equivalent of heat generated per hour is determined by multi-
plying the watt capacity by 3.4 (one watthour is equivalent to 3.413 btu).
The capacities of electric motors are usually expressed in terms of
horsepower instead of watts. If the motor efficiency is known, the watts
input may be calculated from the formula:
= 746 (hp) (7)
n
where
P = motor input, watts.
hp — motor load, horsepower.
n = motor efficiency (expressed as a decimal).
When the motor efficiency is not known the heat equivalent of ej?c^ic?;1
input can be approximately determined by applying data given in 1 able V>.
HEAT GENERATED BY MOTORS
NAMEPLATE EATING HORSEPOWER
TTHUT GAIN IN BTTJ PEE HOUR PEE HORSEPOWER
Connected Load in Same Room
Connected Load Outside of Room
Ysto %
Hto3
3 to 20
4250
3700
2950
1700
1150
400
In the second group belong such appliances as coffee urns, gas ranges,
ste£n tables, broilers, hot plates, etc. For heat generating capacities
of such appliances refer to Table 10.
Considerable judgment must be exercised in the use of data given in
Table 10. Consideration must be given to time of day when appliances
are used and the heat they contribute to the space at time of peak .load.
Only those appliances in use at the time of the peak load need be con-
sidered. Consideration must also be given to the way appliances ar
installed, whether products of combustion are vented to a flue, whethe
products of combustion escape into the space to be conditioned or whethe
appliances are hooded allowing part of the heat to escape through «
stSk?onnected with the hood. There are no generally acceptoi dafe
available on the effects of venting and shielding heating appliances but i
TbeSed tiiat when the appliances are properly hooded wi* a pomtij
fan exhaust system through the hood that 50 per cent of the heat will b^
SnvSed up SS the hood and the balance of 50 per cent will be dissipate.
S the Sac? to be conditioned. Where latent as well as sensible heat i
Sv?n off, h is usually safe to assume that all latent heat will be remove,
by a properly designed and operated vent or hood.
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 10.
HEAT GAIN FROM VARIOUS SOURCES
SOURCE
BTU PK.
s. HOUR
Sensible La
tent Total
Electric Heating Equipment
Electrical Equipment — Dry Heat— No Evaporated \\ ater _ -
Electric Oven — Baking — -
Electric Equipment— Heating Water— Stewing, Boiling, etc
Electric Lights and Appliances per Watt (Dry Heat)_
Electric Lights and Appliances per Kilowatt (Dry Heat) —
Electric Motors per Horsepower
100%
80%
50%
3.4
3413
2546
90%
1200
600
*
*
8000
1025
300
850
3200
*
*
2050
2050
0%
20%
50%
0
0
0
10%
2000
1200
600
*
2000
0
800
0
1300
*
*
0
0
100%
100%
100%
3.4
3413
2546
100%
2400
1200
3400
7500
10000
1025
1100
850
4500
4600
9000
2050
2050
Coffee Urn — Large, IS in. Diameter— Single Drum.— - —
Coffee Urn— Approx. Connected Load per Gallon of Capacity
Electric Range — Small Burner.
Electric Range"" Large Burner - ....... — ~ ...........—-. —
Electric Range — Oven.. - -
Electric Ra.nze— AVarming Compartment — ....... ,- -,., ..
Steam Table— Per Square Foot of Top Surface
Baker's Oven Per Cubic Foot of Volume . --—. ............. ...... ...*——.......
Frying Griddles— Per Square Foot of Top Surface
Hair Dryer in Beauty Parlor— ^600 w
Permanent Wave Machine in Beauty Parlor— 24-25 w Units
Gas Burning Equipment
Gas Equipment — Dry Heat — No Water Evaporated
Gas Heated Oven — Baking. • . -. •— «
90%
67%
50%
12000
5000
*
*
5000
3000
500
2500
400
540
2250
2250
4500
2250
900
540
135
10%
33%
50%
6000
5000
*
*
5000
3000
500
2500
900
60
250
250
500
250
100
60
15
100%
100%
100%
10000
18000
10000
12000
10000
18000
250
100000
100
250
2500
10000
6000
1000
5000
1300
600
2500
2500
5000
3000
3000
1800
3000
1800
5000
3000
5000
2500
1000
600
150
Gas Equipment— Heating Water— Stewing, Boiling, etc
Stove, Domestic Type — No Water Evaporated — Per Medium Size Burner.
Gas Heated Oven*— Domestic Type — -
Stove Domestic Type— Heating Water— Per Medium Size Burner ...„ - -
Residence Gas Range — Giant Burner (About 5J^j in. Diameter*) .. ,-
Residence Gas Range — Medium Burner (About 4 in, Diameter) ,..,
Residence Gas Range — Double Oven (Total Size 18 in. x 18 in. x 22 in. High)
Residence G&s Range— "Pilot . ......—— ....... ...,,„„-,-„ , T,™-,
Restaurant Range— 4 Burners and Oven _. —
Cast-iron Burner — Low Flame — Per Hole....-— ~ —
Cast-iron Burner — High Flame — Per Hole™. ..
Sinnneritjg Burner - — ............
Coffee Urn — Large, 18 in. Diameter— Single Drum
Coffee Urn — Small," 12 I'TV Diameter — Single PT™
Coffee Urn — Per Gallon of Rated Capacity .. .-.
Egg Boiler — Per Egg Compartment —
Steam Table or Serving Table — Per Square Foot of Top Surface ,.- ... r ,,„_
Dish Warmer — Per Square Foot of Shelf,- ^ — ,- -, - -*
Cigar Lighter— Continuous Flame Type- — -
Curling Iron Heater ~ -
Bunsen Type Burner — Large — Natural Gas
Bunsen Type Burner~— Large-— • Artificial Gas..................... ................... ..............
Bunsen Type Burner~~SmalV~~Natural Gas
Bunsen Type Burner — Small — Artificial Gas -,-„ ,-,--,-
Welsbacli "Burner — Natural Gas —
Welsbach Burner — Artificial Gas
Fish-tail Burner — Natural Gas , .,....„,, ^ -, -—-, -, -T
Fish-tail Burner — Artificial Gas. . . — —
Lighting Fixture Outlet — Large, 3 Mantle 480 C.P
Lighting Fixture Outlet — Small, 1 Mantle 160 C.P
One Cubic Foot of Natural Gas Generates
One Cubic Foot of Artificial Gas Generates
One Cubic Foot of Producer Gas Generates- _
Steam Heated Equipment
Steam Heated Surface Not Polished — Per Square Foot of Surface
Steam Heated Surface Polished — Per Square Foot of Surface
330
130
80
400
220
110
2000
1200
2500
300
0
0
0
0
0
0
2000
1200
2500
800
330
130
80
400
220
110
4000
2400
5000
1100
Insulated Surface, Per Square Foot .... ......... _... ...u.^.
Bare Pipes, Not Polished Per Square Foot of Surface.-
Bare Pipes, Polished i*er Square Foot of Surface. ,„
Insulated Pipes, Per Square Foot— . -
Coffee Urn— Large( 18"in. Diameter — "Single PniTTL
Coffee Urn — Small, 12 in. Diameter — Single Drum
Egg Boiler — Per Egg Compartment .. ...
Steam Table — Per Square Foot of Top Surface
Miscellaneous
Heat Liberated By Food per person, as in a Restaurant
Heat Liberated from Hot Water used direct and on towels per hour — Barber Shops |
30
100
30
200
60
300
'"Per cent sensible and latent heat depends upon use of equipment; dry heat, baking or boiling.
160
CHAPTER 8. COOLING LOAD
GENERAL
From the foregoing discussion it is obvious that the determination of
the maximum cooling load is rather complicated by reason of the variable
nature of contributing load components. If the time when the maximum
load occurs is not obvious the load should be calculated for various times
of the day to determine the probable time at which the sum of the various
component loads is a maximum.
Application of the foregoing data in determining cooling load require-
ments is illustrated in Example 1.
Store room
/<-
b
fe
Ceiling height, 12-V
-54-'0"-
8'x6' 14'x6' H'x6'
FIG. 3. PLAN DIAGRAM OF CLOTHING STORE
14'x6'
Example 1. Determine cooling load requirements for a clothing store illustrated in
Fig. 3 and located in Cleveland, Ohio, Latitude 40 deg. This is a one-story building
located on a corner and it faces south and west. Assume building on east and north
sides conditioned.
Wall construction, 8 in. hollow tile, 4 in. brick veneer, plaster on walls, U = 0.33
(Table 4, Wall 38 B, Chapter 5).
Roof construction, 2 in. concrete, % in. rigid insulation, metal lath and plaster
ceiling, U = 0.26 (Table 11, Wall 2 J, Chapter 5).
Floor, maple flooring on yellow pine, no ceiling below, U = 0.34 (Table 8, Wall
1 D, Chapter 5).
Partition, wood lath and plaster on both sides of studding, U = 0.34 (Table 6,
Wall 77 B, Chapter 5).
Show windows, provided with awnings and thin panel partition at rear.
Front doors, 2 ft 6 in. x 7 ft (glass panelled), U - 1.13 (Table 13 A, Chapter 5).
Side door, 3 ft x 7 ft (solid, 1% in. thick), U = 0.51 (Table 13 B, Chapter 5),
Occupancy, 10 clerks, 40 patrons.
Lights, 4200 w.
Outside design conditions, dry-bulb 95 F; wet-bulb 75 F.
Inside design conditions, dry-bulb 80 F; wet-bulb 67 F.
Basement temperature, 85 F.
Store room temperature, 88 F.
161
HEATING VENTHATINO AIR CONDITIONING GUIDE 1938
Solution: The normal heat transmission through various surfaces shown in load
calculations are determined by application of Formula 1.
It is quite obvious from the shape and exposure of this store that the maximum sun
load will exist on the west wall. Since the west wall has a large glass area with a negligible
time lag, the peak load may be expected at 4:00 p.m. at which time, from Table 4,
IG - 182. JG f°r south glass at 4:00 p.m. is 2. Because of the small amount of solar
radiation transmitted through the south glass, the transmission due to temperature
difference has also been included. Assuming time lag in roof and walls to be 2 hours, the
corresponding values for 7 for south and west walls and roof will be those shown in Table
4 for 2:00 p.m. They are respectively 77, 143 and 258. A time lag of 1 hour was assumed
for the west door amounting to I = 192. By substituting these values in equations 2
and 3 the solar heat load is determined.
To determine the heat gain from the outside air it is necessary first to determine the
volume of the outside air to be introduced. Since the show windows are sealed so as not
to permit infiltration and since there are only three doors in this store through which
infiltration can take place, it is obvious that infiltration of air will be a negligible quan-
tity. The volume of the store is 21,600 cu ft. Good practice indicates that in a store
of this character there should be a minimum of from ltol% outside air changes per hour.
On a basis of 1}4 air changes the volume of outside air to be ^introduced would be 32,400
cfh. By reference to Chapter 3 it will be noted that the minimum ventilation require-
ments are 10 cfm per person. On this basis the ventilation requirements would be
30,000 cfh. Since this will produce approximately IJi outside air changes per hour,
30,000 cfh will be considered in this application.
To determine load imposed by occupants it will be found from Table 4, Chapter 3
that the average person standing at rest will dissipate 225 Btu sensible heat and 206
Btu latent heat per hour.
NORMAL TRANSMISSION LOAD:
SURFACE
DIMENSIONS
AREA
SQ FT
U
TEMP. DIFF.
DEGP
BTTJ PBB
HOUR
S Glass
S Wall
W Wall
WDoor
Roof
Floor
N Partition
Total
2(2 ft 6 in. x 7ft) +
2(10 ft x 6 ft)
(30 ft x 12 ft) -155
(GO ft x 12 ft) -321
3 ft x 7 ft
60 ft x 30 ft
26 ft x 54 ft
30 ft x 12 ft
155
205
399
21
1800
1404
360
1.13
0.33
0.33
0.51
0.26
0.34
0.34
15
15
15
15
15
5
8
2,627
1,015
1,975
161
7,020
2,387
979
16,164
SUN LOAD:
SURFACE
DIMENSIONS
AREA
SQ FT
. F
a
JOB
*G
SHADE
FACTOR
BUT PEE
HOUR
SWall
S Glass
W Glass
WDoor
W Wall
Roof
Total
3(14 ft x 6 ft) +
(8 ft x 6 ft)
205
155
300
21
399
1800
0.078
0.118
0.078
0.062
0.7
0.7
0.7
0.9
77
2
182
192
143
258
0.28
0.28
862
87
15,288
333
3,113
25,914
45,597
OUTSIDE AIR HEAT GAIN:
Sensible heat, Hs = 0.24 X 60 d0 Q (tQ - f) (Formula 4).
Q = 50 X 10 = 500 cfm.
Density of air at 95 F dry-bulb and 75 F wet-bulb for a barometric pressure of 29.92 in.
is 0.07089 Ib per cubic foot (Table 4, Chapter 1).
Dew-point of outdoor air is 66 F (psychrometric chart).
162
CHAPTER 8. COOLING LOAD
Partial pressure of vapor is 0.64378 in. Hg. (Pressure of saturated vapor at 66 F,
Table 6, Chapter 1).
a622
°-622
= a°137 lb water vapor per
pound dry air (Formula 5 a, Chapter 1).
- — : - n nlQ- = 0.986 lb dry air per pound outside air.
1 plUS U.Uloi
do = 0.07089 X 0.986 = 0.0699 lb dry air per cubic foot outside air.
H6 =- 60 X 500 X 0.0699 X 0.24 (95-80) - 7549 Btu per hour.
Total heat, H = 60 dQ Q (h0 - K) (Formula 5).
h0 = 38.46 Btu per pound dry air at 75 F wet-bulb (Table 6, Chapter 1).
h = 31.51 Btu per pound dry air at 67 F wet-bulb (Table 6, Chapter 1).
H = 60 X 0.0699 X 500 (38.46 - 31.51) = 14,574 Btu per hour.
Latent heat gain from outside air = 14,574 — 7549 = 7025 Btu per hour.
PEOPLE HEAT GAIN:
50 X 225 = 11,250 Btu per hour, sensible heat.
50 X 206 = 10,300 Btu per hour, latent heat.
LIGHT HEAT GAIN:
4200 X 3.413 = 14,335 Btu per hour.
SUMMARY:
CQMPOHPSNT OF LQAI»
BTU FBI
i HOUB
Sensible
Latent
Normal Transmission Load ..
Sun Load
16,164
45,597
Outside Air Heat Gain..
People Heat Gain— - -
Light Heat Gain !_ .,
7,549
11,250
14,335
7,025
10,300
TotaL -
94,895
17,325
TOTAL LOAD:
94,895 + 17,325
112,220 Btu per hour.
PROBLEMS IN PRACTICE
1 • The outdoor and indoor temperatures are 90 F and 78 F, respectively. What
is the amount of heat transmitted per hour through a 7 ft by 4 ft north window?
Ht = 28 X 1.13 (90-78) « 380 Btu per hour. (Equation 1, Chapter 8 and Table 13 A,
Chapter 5).
2 • a. If a restaurant has two 10 gal gas-heated coffee urns, what is the cooling
load due to them?
b. What is the cooling load due to four 1350 w burners on an electric range?
a. 2 X 10 X 1000 = 20,000 Btu per hour (Table 10).
b. 4 X 1350 - 5400 w - 5.4 kw.
5.4 X 3413 = 18,430 Btu per hour (Table 10).
3 • a. What is the maximum heat transmission for a flat roof located in Pitts-
burgh (latitude 40 deg) exposed to the sun with the outdoor and indoor tem-
163
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
perature 95 F and 80 F, respectively? The roof is of uninsulated 6 in. concrete
with its underside exposed, and -with a black upper surface.
b. What time of day will maximum cooling load due to the roof exist?
a. Ht + Hjt = [A U (t0 - t)] + [A Fal\ (Formulas 1 and 2).
U for roof = 0,64 (Table 11, Wall 4 A, Chapter 5).
F - 0.147 (Fig. 2).
a - 0.9 (Table 6).
/ = 293 (Table 4).
Ht + HR = [1 X 0.64 (95-80)] + [1 X 0.147 X 0.9 X 293] « 48.5 Btu per square
foot per hour.
b. Maximum sun intensity occurs at noon (Table 4). Maximum effect in cooling load
will occur at 3 p.m. (Table 7).
4 • a. What is the maximum rate of heat delivered to a room through a hare
window in the west wall of a building located in New Orleans (30 deg latitude)?
h. What tune of day will it occur?
c. What will maximum rate be if window is protected by awning?
a. HG = AG!G (Formula 3).
7G = 177 (Table 2).
HG = 1 X 177 = 177 Btu per square foot per hour.
6. At 4 p.m. (Table 2).
c. 177 X 0.28 = 49.6 Btu per square foot per hour (Table 8).
5 • What is the heat gain per cubic foot of outside air introduced, under the
following conditions if the barometric pressure is 29.5 in. Hg.?
Outdoor temperatures, 90 F dry-bulb and 75 F wet-bulb.
Inside temperatures, 78 F dry-bulb and 65 F wet-bulb.
Density of air at 90 F dry-bulb, 75 F wet-bulb and 29.5 in Hg. is 0.0705 Ib per cubic foot
(Table 4, Chapter 1).
Dew-point of outdoor air is 68.2 F (psychrometric chart).
Pressure of saturated vapor at 68.2 F is 0.6946 in. Hg. (Table 6, Chapter 1).
W - 0.622 (-JIT?) = 0.622 (29 S^QSQ^ ) " °'°15 lb water vaP°r Per Poun^ dry
air (Formula oa, Chapter 1).
— 0.985 Ib dry air per pound outside air.
j — r-
d0 = 0.0705 X 0.985 = 0.06944 Ib dry air per cubic foot outside air.
Heat content outside dry air at 75 F wet-bulb = 38.46 Btu per pound.
Heat content inside dry air at 65 F wet-bulb = 29.96 Btu per pound.
Total heat, H » 0.06944 (38.46 - 29.96) = 0.59 Btu per cubic foot.
6 • A 7 X 4 ft west window is equipped with an inside aluminum finished
Venetian blind which is adjusted to fully cover the window when the sun shines.
The^net glass area is 75 per cent of the total area of the window. What is the
cooling load due to the window at 10 a.m. and 4 p.m.? Temperatures are:
10 a.m., outside 85 F and inside 77 F; 4 p.m., outside 95 F and inside 80 F.
Latitude 40 deg.
10 a.m.: Ht = 28 X 1.13 (85-77) = 253 Btu per hour (Equation 1, and Table 13A,
Chapter 5).
4 p.m.: 28 X 0.75 = 21 sq ft net glass area.
HG «* 21 X 182 X 0.58 = 2217 Btu per hour (Tables 4 and 8).
164
Chapter 9
FUELS AND COMBUSTION
Classification of Coal, Air for Combustion, Draft Required,
Combustion of Anthracite, Firing Bituminous Coal, Burning
Coke, Hand Firing, Classification and Use of Oil, Classification
and Use of Gas
THE choice of fuel for heating is a question of economy, cleanliness,
fuel availability, operation requirements, and control. The principal
fuels to be considered are coal, oil, and gas.
CLASSinCATION OF COALS
The complex composition of coal makes it difficult to classify it intc
clear-cut types. Its chemical composition is some indication but coals
having the same chemical analysis may have distinctly different burning
characteristics. Users are mainly interested in the available heat pei
pound of coal, in the handling and storing properties, and in the burning
characteristics. A description of the relationship between the qualitiei
of coals and these characteristics requires considerable space; a treatmen
applicable to heating boilers is given in U. S. Bureau of Mines Bulletin 276
A classification of coals is given in Table 1, and a brief description of th<
kinds of fuels is given in the following paragraphs, but it should b
recognized that there are no distinct lines of demarcation between th
kinds, and that they graduate into each other:
Anthracite is a clean, dense, hard coal which creates very little dust in ^ handling. ^ '.
is comparatively hard to ignite but it burns freely when well started. It is non-cakin!
it burns uniformly and smokelessly with a short flame, and it requires little attention 1
the fuel beds between firings. It is capable of giving a high efficiency in the commc
types of hand-fired furnaces. A tabulation of the quality of the various anthraci
sizes will be found in U. S. Bureau of Mines Report of Investigations No. 3283.
Semi-anthracite has a higher volatile content than anthracite, it is not as hard ax
ignites somewhat more easily; otherwise its properties are similar to those of anthracit
Semi-bituminous coal is soft and friable, and fines and dust are created by handling
It ignites somewhat slowly and burns with a medium length of flame.^ Its caking pr
perties increase as the volatile matter increases, but the coke formed is relatively wea
Having only half the volatile matter content of the more abundant bituminous coals
can be burned with less production of smoke, and it is sometimes called smokeless co
The term bituminous coal covers a large range of coals and includes many types havi
distinctly different composition, properties, and burning characteristics. The coals rat
from the high-grade bituminous coals of the East to the poorer coals of the West. Th
caking properties range from coals which completely melt, to those from which 1
volatiles and tars are distilled without change of form, so that they are^ classed as n<
caking or free-burning. Most bituminous coals are strong and non-friable enough
permit of the screened sizes being delivered free from fines. In general, they ign
165
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
easily and burn freely ; the length of flame varies with different coals, but it is long. Much
smoke and soot are possible especially at low rates of burning.
Sub-bituminous coals occur in the western states; they are high in moisture when
mined and tend to break up as they dry or when exposed to the weather; they are liable
to ignite spontaneously when piled or stored. They ignite easily and quickly and have a
medium length flame, are non-caking and free-burning; the lumps tend to break into
small pieces if poked; very little smoke and soot are formed.
Lignite is of woody structure, very high in moisture as mined, and of low heating
value; it is clean to handle. It has a greater tendency than the^sub-bituminous coals to
disintegrate as it dries, and it also is more liable to spontaneous ignition. Freshly mined
lignite, because of its high moisture, ignites slowly. It is non-caking. The char left after
the moisture and volatile matter are driven off burns very easily, like charcoal. The
lumps tend to break up in the fuel bed and pieces of char falling into the ashpit continue
to burn. Very little smoke or soot is formed.
Coke is produced by the distillation of the volatile matter from coal. The type of
coke depends on the coal or mixture of coals used, the temperatures and time of distil-
lation and, to some extent, on the type of retort or oven; coke is also produced as a
residue from the destructive distillation of oil.
TABLE 1. CLASSIFICATION OF COALS BY RANK/
Legend: F.C. = Fixed Carbon. V.M. = Volatile Matter. Btu = British thermal units.
CLASS
GEOUP
LIMITS o? FECED CARBON OR BTU
MINERAL-MATTER-FRBZ BASIS
REQUISITE PHYSICAL
PROPERTIES
i. Meta-anthracite
Dry F.C., 98 per cent or more (Dry
V.M., 2 per cent or less)
I. Anthracite
2 Anthracite
Dry F.C., 92 per cent or more and less
than 98 per cent (Dry V.M., 8 per
cent or less and more than 2 per cent)
Dry F.C., 86 per cent or more and less
than 92 per cent (Dry V.M., 14 per
Non-agglutinating0
3 Semi-anthracite
cent or less and more than 8 per cent)
1 Low volatile bituminous coal —
Dry F.C., 77 per cent or more and less
than 86 per cent (Dry V.M., 23 per
cent or less and more than 14 per
cent)
2. Medium volatile bituminous coal
Dry F,C., 69 per cent or more and less
than 77 per cent (Dry V.M., 31 per
cent or less and more than 23 per
I^_ Bituminous0— '
cent)
3. High volatile A bituminous coal.
Dry F.C., less than 69 per cent (Dry
V.M., more than 31 per cent); and
moist6 Btu, 14,000* or more
4. High volatile B bituminous coal..
Moist* Btu, 13,000 or more and less
than 14,000*
5 High volatile C bituminous coal-
Moist Btu, 11,000 or more and less
than 13,000*
Either agglutinating
or non-weathering*
f
I. Sub-bituminous A coal
Moist Btu, 11,000 or more and less
Both weathering and
|
than 13,000*
non-agglutinating
III. Sub-bituminous.,
2. Sub-bituminous B oo^-l .„.,_ .... ,
Moist Btu 9500 or more and less
than 11,000*
3. Sub-bituminous C coal
Moist Btu 8300 or more and less
than 9500*
:1 T lignite
Moist Btu less than 8300
Consolidated
2 "Rro^ra coal . ri
Moist Btu less than 8300
Unconsolidated
•If agglutinating, classify in low-volatile group of the bituminous class.
*Moist Btu refers to coal containing its natural bed moisture but not including visible water on the
surface of the coal.
•Pending the report of the Subcommittee on Origin and Composition and Metbods of Analysis, it is
recognized that there may be non-caking varieties in each group of the bituminous class.
*Coals having 69 per cent or more fixed carbon on tbe dry, mineral-matter-free basis shall be classified
according to fixed carbon, regardless of Btu.
•There are three varieties of coal in the Higb- volatile C bituminous coal group, namely, Variety 1,
agglutinating and non-weathering; Variety 2, agglutinating and weathering; Variety 3, non-agglutinating
and non-weathering.
/Adapted from .4 .S.T.lf. Standards on Coal and Coke, p. 68, American Society for Testing Materials,
Philadelphia, 1934.
166
CHAPTER 9. FUELS AND COMBUSTION
High-temperature cokes. Coke as usually available is of the high-temperature type,
and contains between 1 and 2 per cent volatile matter. High-temperature cokes are sub-
divided into beehive coke of which comparatively little is now sola for domestic use, by-
product coke, which covers the greater part of the coke sold, and gas-house coke. The
differences among _ these three cokes are relatively small; their denseness and hardness
decrease and friability increases in the order named. In general, the lighter and more
friable cokes ignite and burn the more easily.
Low-temperature cokes are produced at low coking temperatures, and only a portion
of the volatile matter is distilled off. Cokes as made by various processes under develop-
ment have contained from 10 to 15 per cent volatile matter. In general, these cokes
ignite and burn more readily than high-temperature cokes. The properties of various
low-temperature cokes may differ more than those of the various high-temperature cokes
because of the differences in the quantities of volatile matter and because some may be
light and others briquetted.
The sale of petroleum cokes for domestic furnaces has been small and is generally
confined to the Middle West. They vary in the amount of volatile matter they contain,
but all have the common property of a very low ash content, which necessitates the
use of refractory pieces to protect the grates from being burned.
In order to obtain perfect combustion a definite amount of air is re-
quired for each pound of fuel fired. A deficiency of air supply will result
in combustible products passing to the stack unburned, An excess of air
absorbs heat from the products of combustion and results in a greater loss
of sensible heat to the stack.
Total Air Required. The theoretical amount of air required per pound
of fuel for perfect combustion is dependent upon the analysis of the fuel ;
TABLE 2. POUNDS OF AIR PER POUND OF FUEL AS FIRED
ANTHRACITE
Con
Sma-BrruMiNOTJS
BlTUHINOTTS
LlGNTTI
9.6
11.2
11.2
10.3
6.2
however, for estimating purposes the theoretical air required for different
grades of fuel may roughly be taken from Table 2. An excess ^of about
50 per cent over the theoretical amount is considered good practice under
usual operating conditions.
The amount of excess air, based upon the laws of combustion, can be
determined by its relation to the percentage of CO* (carbon dioxide) in
the products of combustion. This relationship is shown by the curves
(Fig. 1) for high and low volatile coals and for coke. In hand-fired fur-
naces with long periods between firings the combustion goes through a
cycle in each period and the quantity of excess air present varies.
Secondary Air. The division of the total into primary and secondary
air necessary to produce the same rate of burning and the same excess air
depends on a number of factors which include size of fuel, depth of fuel
bed, and diameter of firepot. The ratio of the secondary to the primary
air increases with decrease in the size of the fuel pieces, with increase in
the depth of the fuel bed, and with increase in the area of the firepot; the
ratio also increases with increase in rate of burning.
Size of the fuel is a very important factor in fixing the quantity of
secondary air required for non-caking coals. With caking coals it is not
167
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
22
20
18
o
g 14
' I I
YV XjL
\V\
Low-volatile .
./bituminous coa
J High - volatile •_
'bituminous coal
~~20 40 60 80 100 120 140 160
EXCESS AIR, PER CENT
FIG. 1* RELATION BETWEEN C03 AND EXCESS AIR IN GASES OF COMBUSTION
so important because small pieces fuse together and form large lumps.
Fortunately a smaller size fuel gives more resistance to air flow through
the f uel^ bed and thus automatically causes a larger draft above the fuel
bed, which draws in more secondary air through the same slot openings.
In spite of this, ^a small size fuel requires a larger opening of the door
slots; for a certain size for each fuel no slot opening is required, and for
larger sizes too much excess air gets through the fuel bed.
It is impossible to establish a single rule for the correct slot opening for
all types and sizes of fuels and for all rates of burning. Furthermore, the
s
iflojlw
/
s
/
*
s
^
/
/
?
/
'
±J
/
/
/
\
Y
.>
/
/
in
/
w
,<<
7
/
/
/
/
/
>v
/
/
s
/
*
/
/
Sfc
ttdc
*ed
f
/
EATEOFBim
NING, POUNDS PER SQ. FT. PBH HR.
From U. S, Bureau of Mi
nes.
FIG. 2. RELATIVE AMOUNT OF FIRE DOOR SLOT OPENING REQUIRED IN A GIVEN
FURNACE TO GIVE EQUALLY GOOD COMBUSTION FOR HIGH TEMPERATURE
COKE OF VARIOUS SIZES WHEN BURNED AT VARIOUS RATES
168
CHAPTER 9. FUELS AND COMBUSTION
size of slot opening is dependent on whether the ashpit damper is open
or closed. It is better to have too much than too little secondary air; the
opening is too small if there is a puff of flame when the firing door is opened.
Fig. 2, taken from the 17. S. Bureau of Mines Report of Investigations
No. 2980, shows the relationship of the slot opening, for a domestic fur-
nace, to the size of coke and the rate of burning; these openings are with
the ashpit ^damper wide open, and would be less if the available draft
permits of its being partly closed. The same openings are satisfactory for
anthracite.
Bituminous coals require a large amount of secondary air during the
period subsequent to a firing in order to consume the gases and to reduce
the smoke. The smoke produced is a good indicator, and that opening is
best which reduces the smoke to a minimum. Too much secondary air
will cool the gases below the ignition point, and prove harmful instead of
beneficial The following suggestions will be helpful:
1. In cold weather, with high combustion rates, the secondary air damper should be
half open all the time.
2. In very mild weather, with a very low combustion rate, the secondary air damper
should be closed all the time.
3. For temperatures between very mild and very cold, the secondary air damper
should be in an intermediate position.
4. For ordinary house operation, secondary air is needed after each firing for about
one hour.
Draft Requirements
The draft required to effect a given rate of burning the fuel as measured
at the smokehood is dependent on the following factors:
1. Kind and size of fuel.
2. Combustion rate per square foot of grate area per hour.
3. Thickness of fuel bed.
4. Type and amount of ash and clinker accumulation.
5. Amount of excess air present in the gases.
6. Resistance offered by the boiler passes to the flow of the gases.
7. Accumulation of soot in the passes.
Insufficient draft will necessitate additional manipulation of the fuel
bed and more frequent cleanings to keep its resistance down. Insufficient
draft also restricts the control by adjustment of the dampers.
The quantity of excess air present has a marked effect on the draft
required to produce a given rate of burning, and it is often possible to
produce a higher rate by increasing the thickness of the fuel bed.
Combustion of Anthracite1
An anthracite fire should never be poked, as this serves to bring ash to
the surface of the fuel bed where it melts into clinker.
Egg size is suitable for large firepots (grates 24 in. and over) if the fuel
can be fired at least 16 in. deep. The air spaces between the pieces of coal
are large, and for best results this coal should be fired deeply.
lSee reports published by Anthracite Industries Laboratory, Primes, Pennsylvania.
169
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Stove size coal is the proper size of anthracite for many boilers and
furnaces used for heating buildings. It burns well on grates at least 16 in.
in diameter and 12 in. deep. The only instructions needed for burning
this type of fuel are that the grate should be shaken daily, the fire should
never be poked or disturbed, and the fuel should be fired deeply and
uniformly.
Chestnut size coal is in demand for firepots up to 20 in. in diameter, with
a depth of from 10 to 15 in.
Pea size coal is often an economical fuel to burn. It is relatively low
in price. When fired carefully, pea coal can be burned on standard grates.
It is well to have a small amount of a larger fuel on hand when building
new fires, or when filling holes in the fuel bed. Care should be taken to
shake the grates only until the first bright coals begin to fall through the
grates. The fuel bed, after a new fire has been built, should be increased
in thickness by the addition of small charges until it is at least level with
the sill of the fire door. This keeps a bed of ignited coal in readiness
against the time when a sudden demand for heat shall be made on the
heater. A very satisfactory method of firing pea coal consists of drawing
the red coals toward the front end and piling fresh fuel toward the back
of the fire-box.
Pea size coal requires a strong draft and therefore the best results
generally will be obtained by keeping the choke damper open, the cold-
air check closed, and by controlling the fire with the air-inlet damper only.
Pea size can^also be fired in layers with stove or egg size anthracite and
its use in this manner will reduce the fuel costs and attention required.
^ Buckwheat size coal for best results requires more attention than pea
size coal, and in addition the smaller size of the fuel makes it more difficult
to burn on ordinary grates. Greater care must be taken in shaking the
grates than with pea coal on account of the danger of the fuel falling
through the grate. In house heating furnaces the coal should be fired
lightly and^more frequently than pea coal. When banking a buckwheat
coal fire it is advisable after coaling to expose a small spot of hot fire by
putting a poker down through the bed of fresh coal. This will serve to
ignite ^the gas that will be distilled from the fresh coal and prevent an
explosion of gas within the firepot, which in some cases depending upon the
thickness of the bed of fresh coal is severe enough to blow open the doors
and dampers of the furnace. A good draft is required and consequently
the fire is best controlled by the air-inlet damper only. Where frequent
attention can be given and care exercised in manipulation of the grates this
fuel can be burned satisfactorily without the aid of any special equipment.
In general it will be found more satisfactory with buckwheat coal to
maintain a uniform heat output and consequently to keep the system
warm all the time, rather than to allow the system to cool off at times
and then to attempt to burn the fuel at a high rate while warming up. A
uniform low fire will minimize the clinker formation and keep the clinker
in an easily broken up condition so that it readily can be shaken through
the grate.
Forced draft and small mesh grates are frequently used for burning
buckwheat anthracite. For best results and a higher degree of con-
venience, domestic stokers are used.
170
CHAPTER 9. FUELS AND COMBUSTION
No. 2 buckwheat anthracite, or rice size, is used only in domestic
stokers. No. 3 buckwheat anthracite, or barley, has no application in
domestic heating.
Firing Bituminous Coal
Bituminous coal should never be fired over the entire fuel bed at one
time. A portion of the glowing fuel should always be left exposed to
ignite the gases leaving the fresh charge.
Air should be admitted over the fire through a special secondary air
device, or through a slide in the fire door or by opening the fire door
slightly. If the quantity of air admitted is too great the gases will be
cooled below the ignition temperature and will fail to burn. The fireman
can judge the quantity of air to admit by noting when the air supplied
is just sufficient to make the gases burn rapidly and smokelessly above the
fuel bed.
The red fuel in the firebox, before firing, excepting only a shallow layer
of coke on the grate, should be pushed to one side or forward or back-
ward to form a hollow in which to throw the fresh fuel. Some manu-
facturers recommend that all red fuel be pushed to the rear of the firebox
and that the fresh fuel be fired directly on the grate and allowed to ignite
from the top. The object of this is to reduce the early rapid distillation
of gases and to reduce the quantity of secondary air required for smoke-
less combustion.
It is well to have the bright fuel in the firebox so placed that the gases
from the freshly fired fuel, mixed with the air over the fuel bed, pass
over the bed of bright fuel on the way to the flues. The bed of bright
fuel then supplies the heat to raise the mixture of air and gas to the
ignition temperature, thereby causing the gaseous matter to burn and
preventing the formation of smoke.
The fuel bed should be carried as deep as the size of fuel and the
available draft permit, in order to have as much coked fuel as possible
for pushing to the rear of the firebox at the time of firing. A deep fuel
bed allows the longest firing intervals.
If the coal is of the caking kind the fresh charge will fuse into one
solid mass which can be broken up with the stoking bar and leveled from
20 min to one hour after firing, depending on the temperature of the
firebox. Care should be exercised when stoking not to bring the bar up
to the surface of the fuel as this will tend to bring ash into the high
temperature zone at the top of the fire, where it will melt and form
clinker. The stoking bar should be kept as near the grate as possible
and should be raised only enough to break up the fuel. With fuels requir-
ing stoking it may not be necessary to shake the grates, as the ash is
usually dislodged during stoking.
The output obtained from any heater with bituminous coal will usually
exceed that obtainable with anthracite, since soft coal burns more rapidly
than hard coal and with less draft. Soft coal, however, will require
frequent attention to the fuel bed, because it burns unevenly, even
though the fuel bed may be level, forming holes in the fire which admit
too much air, chilling the gases over the fuel bed and reducing the
available draft.
171
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Semi-bituminous coal is fired as bituminous coal, and because of its
caking characteristics it requires practically the same attention. The
Pocahontas Operators Association recommends the central cone method of
firing, in which the coal is heaped on to the center of the bed forming a
cone the top of which should be level with the middle of the firing door.
This allows the larger lumps to fall to the sides, and the fines to remain in
the center and be coked. The poking should be limited to breaking down
the coke without stirring, and to gently rocking the grates. It is recom-
mended that the slides in the firing door be kept closed, as the thinner fuel
bed around the sides allows enough air to get through.
Burning Coke
Coke is a very desirable fuel and usually will give satisfaction as soon
as the user learns how to control the fire. Coke ignites and burns very
rapidly with less draft than anthracite coal. In order to control the air
admitted to the fuel it is very important that all openings or leaks into
the ashpit be closed tightly. A coke fire responds more rapidly than an
anthracite fire to the opening of the dampers. This is an advantage in
warming up the system, but it also makes it necessary to watch the
dampers more closely in order to prevent the fire from burning too rapidly.
A deep fuel bed always should be maintained when burning coke. The
grates should be shaken only slightly in mild weather and should be
shaken only until the first red particles drop from the grates in cold
weather. Since coke weighs only about half as much as anthracite per
cubic foot only about half as much can be put in the firepot, so it will be
necessary to fire oftener. The best size of coke for general use, for small
firepots where the fuel depth is not over 20 in., is that which passes over
a 1 in. screen and through a 1 J^ in. screen. For large firepots where the
fuel can be fired over 20 in. deep, coke which passes over a 1 in. screen and
through a 3 in. screen can be used, but a coke of uniform size is always
more satisfactory. Large sizes of coke should be either mixed with fine
sizes or broken up before using.
Dustless Coal
The practice of treating the more friable coals to allay the dust they
create is increasing. The coal is sprayed with a solution of calcium
chloride or a mixture of calcium and magnesium chlorides. Both these
salts are very hygroscopic and their moisture under normal atmospheric
conditions keeps the surface of the coal damp, thus reducing the dust
during delivery and in the cellar, and obviating the necessity of sprinkling
the coal in the bin.
The coal is sometimes treated at the mine, but more usually by the
local distributor just before delivery. The solution is sprayed under high
pressure, using from 2 to 4 gal or from 5 to 10 Ib of the salt per ton of
coal, depending on its friability and size.
Pulverized Coal
Installations of pulverized coal burning plants in heating boilers are of
the unit type, in which the pulverized coal is delivered into the furnace
immediately after grinding, together with the proper amount of preheated
172
CHAPTER 9. FUELS AND COMBUSTION
air. With ^this apparatus, where the necessary furnace volume is ob-
tainable, high efficiencies can be obtained.
A 150-hp boiler has generally been considered the smallest size for
which pulverized fuel is feasible. Complications are introduced if an
installation with a single boiler has to take care of very light loads.
Hand Firing
Hand firing is the oldest and the most widely used method of burning
coal for heating purposes. To keep the fuel bed in proper condition where
hand firing is used, the following general rules should be observed:
1. Remove ash from fuel bed by shaking the grates whenever fresh fuel is fired. This
removes ash from the fire, enables the air to reach the fuel, and does away with the for-
mation of clinker which is melted ash.
2. Supply the boiler with a deep bed of fuel. Nothing is gained by attempting to
fire a small amount of fuel. A deep bed of fuel secures the most economical results.
3. Remove ash from ashpit at least once daily. Never allow ash to accumulate up
to the grates. If the ash prevents the air from passing through, the grate bars will
burn out and much clinker trouble will be experienced.
The principal requirements for a hand-fired furnace are that it shall have
enough grate area and correctly proportioned combustion space. The
amount of grate area required is dependent upon the desired combustion
rate.
The furnace volume is influenced by the kind of coal used. Bituminous
coals, on account of their long-flaming characteristic, require more space
in which to burn the gases of combustion completely than do the coals
low in volatile matter. For burning high volatile coals provision should
be made for mixing the combustible gases thoroughly so that com-
bustion is complete before the gases come in contact with the relatively
cool heating surfaces. An abrupt change in the direction of flow tends to
mix the gases of combustion more thoroughly. Anthracite requires
practically no combustion space.
CLASSIHCATION OF OILS
Uniform oil specifications were prepared in 1929 by the American Oil
Burner Association, in cooperation with the American Petroleum Institute,
the U. S. Bureau of Standards, the American Society for Testing Materials
and other interested organizations. Oil fuels were classified into six
groups, as indicated by Table 3. When these specifications were prepared,
it was generally accepted that the first three grades were adapted to
domestic use, while the last three were suitable only for commercial and
industrial burners.
^ Today domestic -installations may use No. 4 oil of the so-called heavy
oil group, when and if said oil very closely follows the specifications of
No. 3. Up-to-date listing by the Underwriter's Laboratories should be
referred to before a No. 4 grade of fuel is used which merely meets
Commercial Standards CS 12-35.
Since the specifications as originally drawn provide for maximum limits
only for the several grades, this differentiation has not proved stable.
Realizing how unsatisfactory it is to have specifications which permit the
173
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 3. COMMERCIAL STANDARD FUEL OIL SPECIFICATIONS*
A. Detailed Requirements for Domestic Fuel Oils*
GRADE OF OIL
APPROX.
Bxu
PER
GAL."
FLASH POINT
WATER
AND
SEDIMENT,
MAXIMUM
CARBON
RESIDUE
MAXIMUM
DISTILLATION
TEST
VISCOSITY
MAXIMUM
Min. Max.
Max. 1 Min.
No. 1
Domestic
Fuel Oil
A light distillate
oil for use in
burners requir-
ing a high grade
fuel.
139,000
100 F 150 F
or legal
0.05%
0.02%
10% point
420 F
End point
600 F
No. 2
Domestic
Fuel Oil
A medium distil-
late oil for use
in burners re-
quiring a high
grade fuel.
141,000
125 F 190 F
or legal
0.05%
0.05%
10% point
90% point
620 F
End point
600 F
No. 3
Domestic
Fuel Oil
A distillate fuel
oil for use in
burners where a
low viscosity oil
is required.
143400
150 F i 200 F
or legal'
0.1%
0.15%
90% point
620 F
Saybolt
Universal
at 100 F
70 seconds
•Adapted from "Fuel Oils," p. 2, U. S, Department of Commerce, Bureau of Standards, Commercial
Standard CS18-S5, Washington, 1935.
&POUT Point Maximum is 15 F. Lower or higher pour points may be specified whenever required by
conditions of storage and use. However, these specifications shall not require a pour point less than 0 F
under any conditions.
"Government specifications do not give Btu per gallon, but they are noted here for information only.
B. Detailed Requirements for Industrial Fuel Oils*
GRADE OF On.
APPROX.
BTU
PER
GAL.«
FLASH POINT,
WATER
AND
SEDIMENT,
MAXIMUM
ASH
MAXIMUM
VISCOSITY,
MAXIMUM
Min.
Max.
No. 4.
Industrial Fuel Oil
An oil known to the trade as a light fuel
oil for use in burners where a low vis-
cosity industrial fuel oil is required.
144,500
150 F
See
Note*
1-0%
0.1%
Saybolt
Universal
at 100 F
500 seconds
No. 5
Industrial Fuel Oil
Same as Federal Specifications Board
specification for bunker oil "B" for
burners adapted to the use of indus-
trial fuel oil of medium viscosity.
146,000
150 F
1.0%
0.15%
Saybolt
Furol
at 122 F
100 seconds
No. 6
Industrial Fuel Oil
Same as Federal Specifications Board
specification for bunker oil "C" for
burners adapted to oil of high viscosity
150,000
150 F
2.0%
Saybolt
Furol
at 122 F
300 seconds
«*Pour point may be specified whenever required by conditions of storage and use. However, these
specifications shall not require a pour point less than 15 F under any conditions.
•Whenever required, as for example in burners with automatic ignition, a maximum flash point may
be specified. However, these specifications shall not require a flash point less than 250 F under any con-
ditions.
174
CHAPTER 9. FUELS AND COMBUSTION
substitution of one grade for another, the U. 5. Bureau of Standards in
cooperation with the American Society for Testing Materials is figuring
on a new set of specifications providing for definite limits for each grade.
When these specifications are adopted, it is expected that the National
Board of Fire Underwriters will retest all burners using oils of the maximum
specifications for the grade so that if a burner is approved for a certain
grade it will burn any oil meeting the specifications for that particular
grade.
Several burners adapted to industrial use have recently been listed for
automatic operation with No. 5 oil. Usually oils No. 5 or 6 require
preheating for proper operation, but where conditions are favorable, No.
5 can be used without the equipment that this entails.
There are two reasons for the trend to lower grades of oil. While the
lighter ^oils contain slightly more heat units per pound, the weight per
gallon increases more rapidly than the decrease in heat units per pound,
and oil is bought by the gallon. As a consequence, while a No. 1 oil may
contain 139,000 Btu per gallon, oil No. 5 may test 146,000 Btu per gallon,
or 6 per cent more. Usually there is a differential of 3 to 4 cents between
the No. 1 and No. 5 oils, so that the economy of buying the heavier fuels
is apparent; there remains the economic utilization of the heat content of
the heavier oils.
The cost of oil fuel is dependent also upon the amount that can be
delivered at one time, and the method of delivery. Common practice has
split the tank of the truck delivering oils for domestic use into compart-
ments of 150 to 500-gal capacity, and these unit dumps are made the basis
of price. Where a truck can be connected to a storage-tank fill and
quickly discharge its oil by pump, the price obviously can be less than
where a smaller quantity must be drawn off in 5-gal cans and poured.
For similar reasons an installation that can be supplied from a tank car
on a siding provides for a lower unit fuel cost than one where the oil
must be trucked, even in the large trucks holding 2,000 gal or more that
are used for distributing the heavier oils.
GAS CLASSIFICATION
Gas is broadly classified as being either natural or manufactured.
Natural gas is a mechanical mixture of several combustible and inert
gases rather than a chemical compound. Manufactured gas as dis-
tributed is usually a combination of certain proportions of gases produced
by two or more processes, and is often designated as city gas.
When gas is burned a large amount of water vapor is produced as one
of the products of combustion. This ordinarily escapes up the chimney,
carrying away with it a certain amount of heat. However, when the heat
value of gas is determined in an ordinary calorimeter, this water vapor
is condensed and the latent heat of vaporization that is given up during
the condensation is reported as a portion of the heat value of the gas.
The heat value so determined is termed the gross or higher heat value and
this is what is ordinarily meant when the heat value of gas is specified.
The heat that is reclaimed by the condensation of the water vapor
amounts to about 10 per cent of the total heat value. It is impractical
to utilize the entire higher heat value of the gas in any house-heating
175
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
appliance, because to do so it would be necessary to cool the products of
combustion down below their dew point, which is ordinarily in the
neighborhood of 130 F.
The actual dew point in the chimney is different from the theoretical
value because excess air is admitted not only at the burner but also at the
backdraft diverter which lowers the dew point.
Natural gas is the richest of the gases and contains from 80 to 95
per cent methane, with small percentages of the other combustible
hydrocarbons. In addition, it contains from 0.5 to 5.0 per cent of CO*,
and from 1 to 12 or 14 per cent of nitrogen. The heat value varies from
700 to 1500 Btu per cubic foot, the majority of natural gases averaging
about 1000 Btu per cubic foot. Table 4 shows typical values for the
four main oil fields, although values from any one field vary materially.
Table 4 also gives the calorific values of the more common types of
manufactured gas. Most states have legislation which controls the distri-
bution of gas and fixes a minimum limit to its heat content. The gross
or higher calorific value usually ranges between 520 and 545 Btu per cubic
foot, with an average of 535. A given heat value may be maintained and
yet leave considerable latitude in the composition of the gas so that as
distributed the composition is not necessarily the same in different dis-
TABLE 4. REPRESENTATIVE PROPERTIES OF GASEOUS FUELS,
BASED ON GAS AT 60 F AND 30 IN. HG.
GAS
BnjMBCuFr
SPECIFIC
GBATHT,
Am -
1.00
Ant RxQtnBXD
FOE COMBUS-
TION,
(CuFr)
PRODUCTS or COMBUSTION
THEOBBTZCAL
FLAME TEM-
PEBATUHB,
(DEO FAHB)
TTigh
(Gross)
Low
(Net)
Cubic Feet
ULTI-
MATE
GO*
Dry
Basis
COt
H0
Total
with
N*
Natural gas —
California
1200
1087
0.67
11.26
1.24
2.24
12.4
12.2
3610
Natural gas —
Mid-Conti-
nental
967
873
0.57
9.17
0.97
1.92
10.2
11.7
3580
Natural gas —
Ohio
1130
1025
0.65
10.70
1.17
2.16
11.8
12.1
3600
Natural gas —
Pennsylvania
1232
1120
0.71
11.70
1.30
2.29
12.9
12.3
3620
Retort coal gas
575
510
0.42
5.00
0.50
1.21
5.7
11.2
3665
Coke oven gas
588
521
0.42
5.19
0.51
1.25
5.9
11.0
3660
Carburetted
water gas
536
496
0.65
4.37
0.74
0.75
5.0
17.2
3815
Blue water gas
308
281
0.53
2.26
0.46
0.51
2.8
22.3
3800
Anthracite pro-
ducer gas
134
124
0.85
1.05
0.33
0.19
1.9
19.0
3000
Bituminous
producer gas
150
140
0.86
1.24
0.35
0.19
2.0
19.0
3160
Oil gas
575
510
0.35
4.91
0.47
1.21
5.6
10.7
3725
176
CHAPTER 9. FUELS AND COMBUSTION
tricts, nor at successive times in the same district. There are limits to the
variation allowable, because the specific gravity of the gas depends on its
composition, and too great a change in the specific gravity necessitates a
change in the adjustment of the burners of small appliances.
Table 4 shows that a large proportion of the products of combustion
when gas is burned may consist of water vapor, and that the greater the
proportion of water vapor, the lower the maximum attainable C0$ by gas
analysis. The table also shows that a low calorific value does not neces-
sarily mean a low flame temperature since, for example, natural gas has a
theoretical flame temperature of 3600 F and blue water gas of 3800 F,
although it has a calorific value less than one third that of natural gas.
The quantity of air given in Table 4 is that required for theoretical
combustion, but with a properly designed and installed burner the excess
air can be kept low. The division of the air into primary and secondary
is a matter of burner design and the pressure of gas available, and also of
the type of flame desired.
PROBLEMS IN PRACTICE
1 • Differentiate between the general characteristics of hard and soft coals*
Hard coals contain fixed carbon in large proportions and in addition more ash is present
especially in the smaller sizes. Soft coals have an increasing percentage of carbon in
combination with hydrogen which is volatile and will distill off under high temperature,
producing smoke.
2 • Name several important properties of coal from a utilization standpoint.
a. Caking tendency, whether none, weak, or strong.
b. Quantity of volatile matter.
c. Friability.
d. Fusibility of the ash.
3 • What are the main data commonly available that fix the qualities of coal,
and do these tell the whole story?
a. Calorific value, Btu per pound.
b. Proximate analysis giving percentages of moisture, volatile matter, fixed carbon, ash,
and sulphur.
c. Temperature at which the ash softens.
d. Screen sizes.
Other important qualities not usually given are the friability of the coal, its caking
tendency, and the qualities of the volatile matter. The percentage of ash and its fusion
temperature do not tell how the ash is distributed or how much of it is less fusible lumps
of slate or shale.
4 • Are there available complete and sufficient data on gas and oils to fix their
burning properties and furnace requirements?
Yes. Because gas and oils are of simple and uniform composition, data are available to
fix their burning properties and furnace requirements, but the ability to control their
combustion is somewhat less determinable.
5 • What effect does moisture in fuels have on their efficiency?
With any solid fuel, latent and sensible heat are lost at the stack when moisture is dried
out of the fuel in burning, and when its hydrogen is burned. Therefore, such fuels as
sub-bituminous coal and lignite, which are high in moisture content, have a low efficiency.
However, these efficiencies may be improved if the stack gases are cooled to room tem-
perature, by heating the feed water, for example.
177
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
6 • What are the advantages of a sized fuel for heating furnaces?
Because a sized fuel encourages a more uniform flow of air through the bed, the burning
will be more uniform, and the bed will be less liable to develop holes and will require less
attention. Uniformity of fuel size is more desirable as the area of the bed becomes
smaller; it is less important with fuels that cake, but with sized fuels the caking will be
more uniform and the air flow through the bed will be steadier. In addition, ash and
pieces of slate are less likely to be segregated and to form lumps of clinker.
7 • Does the size of a fuel affect the quantity of air required to burn it at a
given rate?
The total air required to give the same gas analysis at the stack^is independent of the
size of the fuel burned, but for non-caking fuels the ratio of the air passing through the
fuel bed to the total air entering the burner base decreases, for the same^thickness of bed,
as the size of the fuel becomes smaller; this decrease is very rapid for sizes less than one
inch. For coals that cake, this ratio will depend on the way the caked bed is broken up
and on the size of the resulting pieces.
8 • Is the volatile matter which is given off when coals are burned of the same
nature in all coals?
No. The products given off by coals when they are heated differ materially in the ratios
by weight of the gases to the oils and tars. No heavy oils or tars are given off by anthra-
cite, and very small quantities are given off by semi-anthracite. As the volatile matter
in the coal increases to as much as 40 per cent of ash-free and moisture-free coal, in-
creasing amounts of oils and tars are given up. For coals of higher volatile content, the
relative quantity of oils and tars decreases, so it is low in the sub-bituminous coals and
in lignite.
9 • Is smoke a primary product hi the burning of fuels?
Visible smoke may include very small particles of carbon, oil, tar, water (condensed
steam), and ash. Of these, the oils, tars, and ash are mainly primary products, and the
water is partly primary. The carbon, which usually comprises the greater part of the
smoke, results from the breaking up by heat of oils, tars, and such gases as methane, so
it may be considered a secondary product.
10 • Is the sulphur in coals detrimental to combustion?
Not so far as is known, but its complete combustion gives only 25 per cent as much heat
as is given by the same weight of carbon. Sulphur is undesirable because it causes cor-
rosion of flues and stacks, and also because its gases pollute the atmosphere, and damage
buildings and vegetation.
11 • How do deposits of soot on the surfaces of a boiler or heater affect the
quantity of fuel burned?
There are two effects. The scot acts as an insulating layer over the surface and reduces
the heat transmission to the water or air; the Bureau of Mines Report of Investigations
No. 3272 shows that the loss of seasonal efficiency is not as great as has been believed and
should not be over 6 per cent because the greater part of the heat is transmitted through
the firepot. The soot clogs the passages and reduces the draft; the loss of efficiency
from this action may be much more, and also the lack of draft results in unsatisfactory
heating.
178
Chapter 10
CHIMNEYS AND DRAFT CALCULATIONS
Natural Draft, Mechanical Draft, Characteristics of Natural
Draft Chimneys, Determining Chimney Sizes, General Equa-
tion, Chimney Construction, Chimneys for Gas Heating
THE design and construction of a chimney is so important a part
of the heating engineer's work that a general knowledge of draft
characterictics and calculations is essential.
Draft, in general, may be defined as the pressure difference between the
atmospheric pressure and that at any part of an installation through
which the gases flow. Since a pressure difference implies a head, draft
is a static force. While no element of motion is inferred, yet motion
in the form of circulation of gases throughout an entire boiler plant
installation is the direct result of draft. This motion is due to the pressure
difference, or unbalanced pressure, which compels the gases to flow. Draft
is often classified into two kinds according to whether it is created
thermally or artificially, viz, (1) natural or thermal draft, and (2) arti-
ficial or mechanical draft.
Natural Draft
Natural draft is the difference in pressure produced by the difference in
weight between the relatively hot gases inside a natural draft chimney and
an equivalent column of the cooler outside air, or atmosphere. Natural
draft, in other words, is an unbalanced pressure produced thermally by a
natural draft chimney as the pressure transformer and a temperature
difference. The intensity of natural draft depends, for the most part,
upon the height of the chimney above the grate bar level and also the
temperature difference between the chimney gases and the atmosphere.
A typical natural draft system consists essentially of a relatively tall
chimney built of steel, brick, or reinforced concrete, operating with the
relatively hot gases which have passed through the boilers and accessories
and from which all the heat has not been extracted. Hot gases are an
essential element in the operation of a natural draft system, although
inherently a heat balance loss.
A natural draft chimney performs the two-fold service of assisting in
the creation of draft by aspiration and also of discharging the gases at an
elevation sufficient to prevent them from becoming a nuisance.
Natural draft is quite advantageous in installations where the total loss
of draft due to resistances is relatively low and also in plants which have
practically a constant load and whose boilers are seldom operated above
179
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
their normal rating. Natural draft systems have been, and are still being,
employed in the operation of large plants during the periods when the
boilers are operated only up to their normal rating. When the rate of
operation is increased above the normal rating, some form of mechanical
draft is employed as an auxiliary to overcome the increased resistances or
draft losses. Natural draft systems are used almost exclusively in the
smaller size plants where the amount of gases generated is relatively small
and it would be expensive to install and operate a mechanical draft
system.
The principal advantages of natural draft systems may be summarized
as follows: (1) simplicity, (2) reliability, (3) freedom from mechanical
FIG. 1. GENERAL OPERATING CHARACTERISTICS OF TYPICAL INDUCED DRAFT FAN
parts, (4) low cost of maintenance, (5) relatively long life, (6) relatively
low depreciation, and (7) no power required to operate. The principal
disadvantages are: (1) lack of flexibility, (2) irregularity, (3) affected
by surroundings, and (4) affected by temperature changes.
Mechanical Draft
^Artificial draft, or mechanical draft, as it is more commonly called, is a
difference in pressure produced either directly or indirectly by a forced
draft fan, an induced draft fan, or a Venturi chimney as the pressure
transformer. The intensity of mechanical draft is dependent for the most
part upon the size of the fan and the speed at which it is operated. The
element of temperature does not enter into the creation of mechanical
draft and therefore its intensity, unlike natural draft, is independent of the
temperature of the gases and the atmosphere. Mechanical draft includes
the induced and Venturi types of draft systems in which the pressure
difference is the result of a suction, and also the forced draft system in
which the pressure difference is the result of a blowing. Mechanical draft
systems^tend to produce a vacuum or a plenum, as the system used in its
production creates a pressure difference below, or above, atmospheric
1RO
CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS
1
,
410
X1
"^
»ij
5jn
\
^
*S'
A
K
4OO
/
^
(i?>
^
w
fl.
380
ff1
&
^
•"*
^
aeo
^
»-,
S
s
s
.-. u
§
/
^
w
V
^
•34O
z
^
*s
^
**
V
w
it.
£
s
60 ?
2320
j.
n*
S i
o
oe
x
•\r
30O
m
^
\
>
0.
/
\
J0«
290
/
X
-BO-
260
/
%
j
C
K>
4C
0
45
O
50
0
V*
0
•C
0 «j
to
FIG. 2. OPERATING CHARACTERISTICS OF TYPICAL CENTRIFUGAL PUMP
pressure, respectively. A mechanical draft system may be used either in
conjunction with, or as an adjunct to, a natural draft system.
Draft Control
To obtain the maximum efficiency of combustion, a definite minimum
supply of air to the combustion chamber must be maintained. To pro-
vide this condition, it is necessary to have some mechanical means of
draft control or adjustment, because of variable wind velocities, fluctua-
tions in atmospheric temperatures and barometric pressures, and their
effect upon draft.
For this purpose there are various mechanical devices which auto-
matically control the volume of air admitted to the combustion chamber.
Mechanical draft regulators designed to control or adjust draft, should
1.4
1.2
1.1
S
|0.8
307
*±0.6
005
.£
§0.4
03
0.2
0.1
°c
— — ^
***•*,
\
4*,
i
fe
%;
^
V
ps
***
.— — '
=x
*- -N
"•x^
ff>c
^
s^
\
\
¥
\
s.
\j
/
\
V
\
/
\
\
\
/
\
^
\
/
\
,\
/
\
\
^
A
) 30 60 90 120 150 180 210 240 270 30(
Amount of Gases Flowing and Discharged, H>. per sea, W
FIG. 3. TYPICAL SET OF OPERATING CHARACTERISTICS OF A NATURAL DRAFT CHIMNEY
181
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
not be confused with mechanical draft systems that create draft mechani-
cally, but which must also be automatically controlled.
The use of such a device to provide a more uniform and dependable
control of draft than could be maintained by manually operated dampers,
will produce better combustion of fuel. This higher efficiency of combus-
tion together with the reduced heat losses up the chimney by reason of
decreased gas velocity, results in fuel economy, with consequent lower
costs of plant operation.
CHARACTERISTICS OF CHIMNEYS
In order to analyze the performance of a natural draft chimney, it may
be advantageous to compare its general operating characteristics with
those of a centrifugal pump and also of a centrifugally-induced draft fan,
there being a similarity among the three. Figs. 1, 2 and 3 show the
general operating characteristics of a typical centrifugally-induced draft
fan, a typical centrifugal pump, and a typical natural draft chimney,
respectively. The draft-capacity curve of the chimney corresponds to
the head-capacity curve of the pump and also to the dynamic-head
capacity curve of the fan.
When the gases in the chimney are stationary, the draft created is
termed the theoretical draft. When the gases are flowing, the theoretical
intensity is diminished by the draft loss due to friction, the difference
between the two being termed the total available draft. The general
equation for this net total available draft intensity of a natural draft
chimney with a circular section is as follows:
D -2Qfim? (W* W*\ 0-00126 W»7V/£ m
Pa - 2.9ftOT0 (jr-jr) ^^ (D
where
D& = available draft, inches of water.
H — height of chimney above grate bars, feet.
BQ ~ barometric pressure corresponding to altitude, inches of mercury.
W0 = unit weight of a cubic foot of air at 0 F and sea level atmospheric pressure,
pounds per cubic foot.
Wc — unit weight of a cubic foot of chimney gases at 0 F and sea level atmospheric
pressure, pounds per cubic foot.
To « absolute temperature of atmosphere, degrees Fahrenheit.
TC =» absolute temperature of chimney gases, degrees Fahrenheit.
W — amount of gases generated in the combustion chamber of the boiler and passing
through the chimney, pounds per second.
/ ~ coefficient of friction.
L = length of friction duct of the chimney, feet.
D = minimum diameter of chimney, feet.
The first term of the right hand expression of Equation 1 represents
the theoretical draft intensity, and the second term, the loss due to friction.
Example 1. _ Determine the available draft of a natural draft chimney 200 ft in height
and 10 ft in diameter operating under the following conditions: atmospheric tempera-
ture, 62 F; chimney gas temperature, 500 F; sea level "atmospheric pressure, B0 = 29.92
in. of mercury; atmospheric and chimney gas density, 0.0863 and 0.09, respectively;
coefficient of friction, 0.016; length of friction duct, 200 ft. The chimney discharges
100 Ib of gases per second.
182
CHAPTER 10. CHIMNEYS AND DRAFT CALCUUITIONS
Substituting these values in Equation 1 and reducing:
2.96 X 200 X 29.92 X
0863 Q.09\ 0.00126 X 100* X 960 X 0.016 X 200
/0.086S
\ 522
960 /
10* X 29.92 X 0.09
1.27 - 0.14 ~ 1.13 in.
Fig. 3 shows the variation in the available draft of a typical 200 ft by
10 ft chimney operating under the general conditions noted in Example 1.
When the chimney is under static conditions and no gases are flowing, the
available draft is equal to 1.27 in. of water, the theoretical intensity. As
the amount of gases flowing increases, the available intensity decreases
until it becomes zero at a gas flow of 297 Ib per second, at which point the
draft loss due to friction is equal to the theoretical intensity. The draft-
capacity curve corresponds to the head-capacity curve of centrifugal
ou
29
£28
•5
.£27
§26
£ 25
£24
| 23
m 22
21
20
X
'V,.
\
\
s
\
,.
X
^
^
s^
s>v
*-x
) 1000 2000 3000 4000 5000 6000 70C
Corresponding Altitude above Sea Level, ft
FIG. 4. RELATION BETWEEN BAROMETRIC PRESSURE AND ALTITUDE
pump characteristics and the dynamic-head-capacity curve of a fan. The
point of maximum draft and zero capacity is called shut-off draft, or point
of impending delivery, and corresponds to the point of shut-off head of a
centrifugal pump. The point of zero draft and maximum capacity is
called the wide open point and corresponds to the wide open point of a
centrifugal pump. A set of operating characteristics may be developed
for any size chimney operating under any set of conditions by substituting
the proper values in Equation 1 and then plotting the results in the
manner shown in Fig. 3.
In substituting the values for the various factors in Equation 1, care
should be exercised that the selections be as near the actual conditions as
is practically possible. The following notes will serve as a guide for these
selections:
1. The barometric pressure varies inversely as the altitude of the plant above sea level
Fig. 4 gives the barometric pressure corresponding to various elevations as computec
from the equation :
where
En - 62,737 logi
= altitude of plant above sea level, feet.
183
(2
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
In general, the barometric pressure decreases approximately 0.1 in. of mercury per 100
ft increase in elevation.
2. The unit weight of a cubic foot of chimney gases at 0 F and sea level barometric
pressure is given by the equation:
Wc « 0.131 CO, -f 0.095 02 -f 0.083 Nt (3)
In this equation CO^ O* and Nt represent the percentages of the parts by volume of the
carbon dioxide, oxygen and nitrogen content, respectively, of the gas analysis. For
ordinary operating conditions, the value of Wc may be assumed at 0.09.
The density effect on the chimney gases due to superheated water vapor resulting
from moisture and hydrogen in the fuel, or due to any air infiltrations in the chimney
proper are here disregarded. Though water vapor content is not disclosed by Orsat
analysis, its presence tends to reduce the actual weight per cubic foot of chimney gases.
3. The atmospheric temperature is the actual observed temperature of the outside air
at the time the analysis of the operating chimney is made. The mean atmospheric
temperature in the temperate zone is approximately 62 F.
4. The chimney gas^ temperature does not vary appreciably from the gas temperature
as it leaves the breeching and enters the chimney. For average operating conditions, the
chimney gas temperature will vary between 500 F and 650 F except in the case when
economizers and recuperators are used, when the temperature will vary between 300 F
and 450 F. If a chimney has been properly constructed, properly lined and has no air
infiltration due to open joints, the temperature of the gases throughout the chimney will
not differ appreciably from the foregoing figures. In most up-to-date heating plants, the
temperature may be read from instruments or ascertained from a pyrometer. The
analysis of this section is predicated on the assumption of constant gas temperature and
no air infiltration throughout the height of the chimney.
5. The coefficient of friction between the chimney gases and a sooted surface has been
taken by many workers in this field as a constant value of 0.016 for the conditions in-
volved. This value, of course, would be less for a new unlined steel stack than for a
brick or brick-lined chimney, but in time the inside surface of all chimneys regardless of
the materials of construction becomes covered with a layer of soot, and thus the coef-
ficient of friction has been taken the same for all types of chimneys and in general
constant for all conditions of operation. For reasons of simplicity and convenience to
the^reader, this constant value of 0.016 has been employed in the development of the
various special equations and charts shown in this chapter.
However, much to be recommended as an alternate method is the practise of separ-
ately determining duct friction factors as a function of the flow conditions, specifically
as a function of the Reynolds number and the relative duct roughness. The Reynolds
criterion is based on the physical properties of the gas, the duct dimensions, and the gas
velocity. The gas velocity for a chimney is usually well above the critical velocity.
It is likely that this procedure of using a separately determined variable friction factor
for chimney flow will give results that are to be preferred over those based on a set
constant.
The Reynolds number, a dimensionless ratio, may be stated as follows:
. Cr=^ (4)
where
D = chimney diameter, feet.
V - velocity of hot gas, feet per second,
p = mass density of the chimney gas per cubic foot.
(i = viscosity of the gas in pounds-second per square foot taken at the gas tem-
perature.
In another form:
1.27 W 0.039617
184
CHAPTER 10. CHIMNEYS AND DRAFT CALCUIATIONS
where
weight of gas passed per second.
acceleration of gravity.
The value of jj, for chimney gases is usually taken as that of air or nitrogen, and for the
variation of p, with temperature, the Sutherland equation may be employed as follows,
giving n in pounds-second per square foot:
f273 + C\ f Tc
^ " ^ Lrc + cj L273
where
Tc — chimney gas temperature, degrees Centigrade.
pLo = gas viscosity at 0 C.
C — constant for specific gas.
Using International Critical Table values, for air
nitrogen IK> = 34.5 X 10-8; and C = 110.
35.6 X 10-8; C = 12-4; for
0.010
0.001
40 60 80 100 200
REYNOLDS NUMBER, IN THOUSANDS
FIG. 5. VARIATION OF FRICTION FACTOR / WITH REYNOLDS NUMBER
Values for the viscosity of air and of nitrogen (the principal component of chimney
gases) for the different temperatures follow, in which the values given in pounds-second
per square foot are to be multiplied by 10-8:
Temp. F
Air
Nitrogen
300
49.7
47.7
400
54.5
52.2
500
58.5
56.0
600
62.5
59.8
700
66.7
63.5
800
70.5
67.0
Example 2. To determine the Reynolds number Cr for a flow of 118 Ib gas per second
up a 12 ft diameter chimney at a temperature of 500 F. The gas may be assumed to
have the same viscosity as nitrogen at 500 F. Using Equation 5 :
n AO™
= 0.0396 =
°-0396 X 118
12
x
The variation of the friction factor/ with the Reynolds number is shown in Fig. 51.
Three curves are shown: A, B, and C, where the choice of the friction factor curve
depends on the relative surface roughness, and this for usual chimney construction may
iSee also Flow of Fluids in Closed Circuits, by R. J. S. Pigott (Mechanical Engineering, August, 1933).
185
HEATING VENTIIATINO AIR CONDITIONING GUIDE 1938
be selected by size since surface conditions in service are always undetermmant. For
sizes up to 3 ft in diameter, Curve C may be used; from 3 to 6 ft, Curve B ; and from 6 ft
upwards, Curve A. Thus for the previous example with CT = 698,000 and 12 ft diameter,
/ would be taken from Curve A as 0.0039.
6. The length of the friction duct is the vertical distance between the bottom of the
breeching opening and the top of the chimney. Ordinarily this distance is approximately
equal to the height of the chimney above the grate level.
.001 .002 .003 .004 .005 .006
Available Draft per Ft of Height, in. of Water
.007
FIG. 6. CHIMNEY PERFORMANCE CHART*
*ro scive a typical example: Proceed horizontally from a Weight Flow Rate point to intersection with
diameter line; from this intersection follow vertically to chimney height line; from this intersection follow
horizontally to the right to Available Draft scale. Starting from a point of Available Draft, take steps in
reverse order.
7. Assuming no air infiltration the amount of gases flowing and being discharged is,
of course, equal to the amount of gases generated in the combustion chamber of the
boiler. The total products of combustion in pounds per second for a grate-fired boiler
may be computed from the equation:
W -
where
3600
(6)
C& = pounds of fuel burned per square foot of grate surface per hour.
G ~ total grate surface of boilers, square feet.
Cg X G = total weight of fuel burned per hour.
Wtp = total weight of products of combustion per pound of fuel.
A similar computation may be made in the case of gas, oil, or stoker-fired fuel.
186
CHAPTER 10. CHIMNEYS AND DRAFT CALCUI»ATIONS
Fig; 6 Is a typical chimney performance chart giving the available draft
intensities for various amounts of gases flowing and sizes of chimney.
This chart is based on an atmospheric temperature of 62 F, a chimney gas
temperature of 500 F, a unit chimney gas weight of 0.09 Ib per cubic foot,
sea level atmospheric pressure, a coefficient of friction of 0.016, and a
friction duct length equal to the height of the chimney above the grate
level. These curves may be used for general operating conditions. For
specific operating conditions, a new chart should be constructed from
Equation 1.
It has been the usual custom, and still is to a lamentably great extent,
to select the required size of a natural draft chimney from a table of
chimney sizes based only on boiler horsepowers. After the ultimate
horsepower of the projected plant had been determined, the chimney size
in the table corresponding to this figure was then selected as the proper
size required. Generally, no further attempt was made to determine if
the height thus selected was sufficient to help create the required draft
demanded by the entire installation, or the diameter sufficiently large to
enable the chimney quickly, efficiently, and economically to dispose of the
gases. Since the operating characteristics of a natural draft chimney are
similar in all respects to those of a centrifugal pump, or a centrifugal fan,
it is no more possible to select a proper size chimney from such a table,
even with correction factors appended, than it is to select the proper size
pump from tables based only on the amount of water to be delivered.
DETERMINING CHIMNEY SIZES
The required diameter and height of a natural draft chimney are given
by the following equations:
V* (7)
D - 0.288 J WTc (8)
* B0WCV
where
H = required height of chimney above grate bar level, feet.
D = required minimum diameter of chimney, feet (constant for entire height),
V = chimney gas velocity, feet per second.
pr = total required draft demanded by the entire installation outside of the chimney,
inches of water.
Equations 7 and 8 give the required size of a natural draft chimney with
all of the operating factors taken into consideration. Values for all of the
factors with the exception of the chimney gas velocity may be either
observed or computed. It is, of course, necessary to assume an arbitrary
value for the velocity in order to arrive at some definite size. For any one
set of operating conditions tjiere will be as many sizes of chimneys as there
are values of reasonable velocities to assume. Of the number of sizes
corresponding to the various assumed velocities, there is one size which
will be least expensive. Since the cost of a chimney structure, regardless
187
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
of the kind of material used in the construction, varies as the volume of
material in the structure, the cost criterion then may be represented by
the approximate equation :
Q = ttHD (9)
where
Q - volume of material, cubic feet.
t — average wall thickness, feet.
For all practical purposes, the value of xt may be taken as a constant
regardless of the size of the structure. Hence, in general, the volume, and
consequently the cost, of a chimney structure may be based on the factor
HD as a criterion. Therefore, the value of the chimney gas velocity which
will result in the least value of HD for any one set of operating con-
ditions will produce a structure which will be the most economical to use,
because its cost will be least.
The problem at hand is to deduce an equation for the chimney gas
velocity which will result in a combination of a height and a diameter
whose product HD will be least. The solution is obtained by equating the
product of Equations 7 and 8 to HD, differentiating this product with
respect to V and equating the resulting expression to zero. This pro-
cedure results in the following expression :
772r Q c 2/5
_TO"
" \
where Fc — economical chimney gas velocity, feet per second.
Equation 10 gives the economical velocity of the chimney gases for
any set of operating conditions, and represents the velocity which will
result in a chimney the size of which will cost less than that of any other
size as determined by any other velocity for the same operating con-
ditions. After the value of the economical velocity has been determined,
the corresponding height and diameter can then be determined from
Equations 7 and 8, respectively, and the economical size will then be
attained. Equations 7, 8 and 10 may be simplified considerably for
average operating conditions in an average size steam plant by assuming
typical conditions.
Average chimney gas temperature, 500 F ....... __________________ Tc = 960
Mean atmospheric temperature, 62 F _____ ......................... TQ = 522
Average coefficient of friction, 0.016 ____________________________________ ./ — 0.016
Average chimney gas density, 0.09. ________________________________ Wc = 0.09
Sea level elevation, with barometer of 29.92 _____ ............... B0 - 29.92
Substituting these values in Equations 10, 8 and 7, respectively, and
reducing, the results are substantially:
- (11)
D - 1.5T72/5 (12)
H = 1901>r (13)
188
CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS
Fig. 7 gives the economical chimney sizes for various amounts of gases
flowing and for required draft intensities as computed from Equations 11,
12 and 13. They are based on the operating factors used in reducing
Equations 7, 8 and 10 to their simpler form. The sizes shown by the
curves in the chart should be used for general operating conditions only,
or for installations where the required data necessary for an exact deter-
Height of Chimney, ft.
^0 25 50 75 100 125 150 1 75 200 225 250 275 300 325 350 371
01234
5 6 7 8 9 10 11 12
Diameter of Chimney, ft
13 14 15°
FIG. 7. ECONOMICAL CHIMNEY SizEsa
aDiameter values also for gas temperatures of 400, 500 and 600 F
mination are difficult or impossible to secure. Whenever it is possible to
secure accurate data, or the anticipated operating conditions are fairly
well known, the required size should be determined from Equations 7,
8 and 10. The recommended minimum inside dimensions and heights of
chimneys for small and medium size installations are given in Table 1.
GENERAL EQUATION
The general draft equation for a steam producing plant may be stated
as follows:
0t - Af - *F + AB -h ted + feC + feBr + &V + ho + &B + &R (14)
189
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
where
Dt » theoretical draft intensity created by pressure transformer, inches of water.
/?f = draft loss due to friction in pressure transformer, inches of water.
feF = draft loss through the fuel bed, inches of water.
&B = draft loss through the boiler and setting, inches of water.
JiEr = draft loss through the breeching, inches of water.
kv — draft loss due to velocity, inches of water.
&Bd = draft loss due to bends, inches of water.
he = draft loss due to contraction of opening, inches of water.
ho = draft loss due to enlargement of opening, inches of water.
&E == draft loss through the economizer, inches of water.
&R = draft loss through recuperators, regenerators, or air heaters, inches of water.
The left hand member of Equation 14 represents the total amount of
available draft created by the pressure transformer, that is, the natural
draft chimney, Venturi chimney, or fan, and is equal to the theoretical
intensity less the internal losses incidental to operation. The right hand
member represents the sum of all of the various losses of draft throughout
the entire boiler plant installation outside of the pressure transformer
itself. The left hand member expresses the available intensity and is
analogous to the head developed by a centrifugal pump in a water works
system, while the right hand member expresses the required draft in-
tensity and is analogous to the total dynamic head in a water works
system. For a general circulation of gases
AL - Dr (15)
where
.Da — available draft intensity, inches of water.
Pr = required draft, inches of water.
The draft loss through the fuel bed (ftp), or the amount of draft required to
effect a given or required rate of combustion, varies between wide limits
and represents the greater portion of the required draft. In coal-fired
installations, the draft loss through the fuel bed is dependent upon the
following factors: (1) character and condition of the fuel, clean or dirty;
(2) percentage of ash in the fuel; (3) volume of interstices in the fuel bed,
coarseness of fuel; (4) thickness of the fuel bed, rate of combustion;
(5) type of grate or stoker used; (6) efficiency of combustion.
There is a certain intensity of draft with which the best results will be
obtained for every kind of coal and rate of combustion. Fig. 8 gives the
intensity of draft, or the vacuum in the combustion chamber required to
burn various kinds of coal at various rates of combustion. Expressed in
other words, these curves represent the amount of draft required to force
the necessary amount of air through the fuel bed in order to effect various
rates of combustion. It will be noted that the amount of draft increases
as the percentage of volatile matter diminishes, being comparatively low
for the lower grades of bituminous coals and highest for the high grades
and small sizes of anthracites. Also, when the interstices of the coal are
large and the particles are not well broken up, as with bituminous coals,
much less draft is required than when the particles are small and are well
190
CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS
broken up, as with bituminous slack and the small sizes of anthracites. In
general, the draft loss through the fuel bed increases as: (1) the per-
centage of volatile matter diminishes; (2) the percentage of fixed carbon
increases; (3) the thickness of the bed increases; (4) the percentage of ash
increases; (5) the volume of the interstices diminishes.
In making the preliminary assumptions for the draft loss through the
fuel bed, due allowances should be made for a possible future change in
the grade of fuel to be burned and also in the rate of combustion. A value
TABLE 1.
RECOMMENDED MINIMUM CHIMNEY SIZES FOR
HEATING BOILERS AND FURNACES*
RECTANGULAR FLUB
ROUND FLTIK
WARM Am
STEAM
TTT ^
NOMINAL
FtJRNACl
CAPACITY
or LEADER
PTPB
BOILER
CAPACITY
SQFr
OF RADI-
ATION
WATER
HEATER
CAPACITY
or RADI-
ATION
DIMEN-
SIONS or
FlRVCliAT
LINING
IN INCHES
Actual
Inside
of Fire Clay
Actual
Area
Sq In.
Inside
Diam-
eter of
Lining
in
Actual
Area
Sq In.
HEIGHT
IN FT
ABOTV
GRATJB
in Inches
Inches
790
590
973
8^x13
7 xllJi
81
35
1000
690
1,140
10
79
900
1,490
13x13
HJixllJi
127
900
1,490
8^x18
6?4 x 16j2
110
1,100
1,820
12
113
40
1,700
2,800
13x18
HJ^xl6J-i
183
1,940
3,200
15
177
2,130
3,520
18x18
15Jixl5Ji
248
2,480
4,090
20x20
17J^xl7}i
298
45
3,150
5,200
18
254
50
4,300
7,100
20
314
4,600
7,590
20x24
17x21
357
5,000
8,250
24x24
21x21
441
55
5,570
9,190
24x24°
576
60
5,580
9,200
22
380
6,980
11,500
24
452
65
7,270
12,000
24x28b
672
8,700
14,400
28x28b
784
9,380
15,500
27
573
10,150
16,750
30x30b
900
10,470
17,250
28x32b
896
aTbis table is taken from the A.S.H.V.E. Code of Minimum Requirements for the Heating and Venti-
lation of Buildings (Edition of 1929).
bDimensions are for unlined rectangular flues,
should be selected for this loss which will represent not only the highest
rate of combustion which will be encountered, but also the grade of coal
which has the greatest resistance through the fuel bed and which may be
burned at a later date.
In powdered-fuel and oil-fired installations, there will be no draft loss
through the fuel bed since there is none and, consequently, this factor
becomes zero in the general draft equation. All other factors being
constant, the height of the chimney in installations of this character will
be less than the height in coal-fired installations, and in the case of me-
chanical draft installations the driving units need not be as large since the
head against which the fan is to operate is not as great in the former as
in the latter.
191
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
The draft loss through the boiler and setting (As) also varies between wide
limits and, in general, depends upon the following factors:
1. Type of boiler. 5. Arrangement of baffles.
2. Size of boiler. 6. Type of grate.
3. Rate of operation. 7. Design of brickwork setting.
4. Arrangement of tubes. 8. Excess air admitted.
9. Location of entrance into breeching.
Curves showing the draft loss through the boiler are usually based on
the load or quantity of gases passing through the boiler, expressed in
terms of percentage of normal rate of operation. Owing to the great
variety of boilers of different designs and the various schemes of baffling,
it is impossible to group together a set of curves for the draft loss through
0 5 10 15 20 25 30 35 40 45
POUNDS OF COAL BURNED PER SQ FT OF GRATE SURFACE PER HOUR
FIG. 8. DRAFT REQUIRED AT DIFFERENT RATES OF COMBUSTION
FOR VARIOUS KINDS OF COAL
the boiler which may even be used generally. It is therefore necessary to
secure this information from the manufacturer of the particular type of
boiler and baffle arrangement under consideration.
When a boiler is installed and in operation, the draft loss depends upon
the amount of gases flowing through it. This, in turn, depends upon the
proportion of excess air admitted for combustion. Primarily, the amount
of excess air is measured by the COZ content; the less the amount of C02,
the greater the amount of excess air and hence the greater the draft loss.
The loss of draft through the boiler will vary directly as the size of the
boiler and the length of the gas passages within. The loss also varies as
the number of tubes high, but not in a direct ratio inasmuch as the loss
due to the reversal of flow at the ends of the baffles remains constant
regardless of the height of the boiler. The arrangement of the tubes,
whether the gases flow parallel to or at right angles to the tubes, has an
appreciable effect on the loss. The arrangement of the baffles influences
the draft loss greatly, the loss through a boiler with five passes being
192
CHAPTER 10. CHIMNEYS AND DRAFT CAIICULATIONS
greater than the loss through one of three or four passes. A poor design
and a rough condition of the brickwork will increase the loss greatly,
whereas a proper design and a smooth condition will keep the loss at a
minimum. The loss through the boiler will be less when the breeching
entrance is located at or near the top of the boiler than when it is located
at or near the bottom since the gases have a shorter distance to travel
in the former instance.
The draft loss through the breeching (&Br) is given by the general
equation :
where
W = the amount of gases flowing, pounds per second.
Tc = absolute temperature of breeching gases, degrees Fahrenheit.
/ = coefficient of friction.
L — length of breeching, feet.
A = area of breeching, square feet.
BQ = atmospheric pressure corresponding to altitude, inches of mercury.
Wc = weight of a cubic foot of breeching gases at 0 F and sea level atmospheric
pressure; pounds per cubic foot.
Cbr = hydraulic radius of breeching section.
It has been the general custom to lump off the intensity of the breeching
loss at 0.10 in. of water per 100 ft of breeching length regardless of its size
or shape or the amount and temperature of the gases flowing through it.
This practice is hazardous and has no more foundation in fact than that of
determining the friction head in a water works system without taking
into consideration the size of the pipe or the amount of water flowing
through it. When the length of the breeching is relatively short, any
variation in any one of the factors in the equation will have no appreciable
effect on the draft loss. However, when the breeching is relatively long,
the draft loss is affected greatly by the various factors, particularly by the
size and shape as well as by the weight of gases flowing.
The draft loss due to velocity (hv) is given by the equation
0.000194W»rc
hv =
and represents the amount of draft required to accelerate the gases from
zero velocity to the velocity at which the gases are flowing, or in other
words, from a static gas condition of zero flow to the amount of gases
flowing throughout the installation. This loss corresponds to the velocity
head in water works systems.
The draft loss due to bends (&Bd) is equivalent to the loss due to the
velocity head for a 90-deg bend. In changing direction of flow, the gas
velocity decreases to zero with a loss of velocity head and then increases
to its proper value at the expense of a loss in pressure head, the net result
being a loss in pressure head equal to the velocity head at the bend.
This loss is given by the equation:
193
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
The friction at a right-angle bend is sometimes expressed as the
equivalent of a straight length of flue of a certain length for a certain
diameter, similar to the procedure used in estimating the loss due to
bends in piping systems conducting water. Most flues, however, par-
ticularly breechings, are built square or rectangular in section and no
general equation based on the shape of the flue can be conveniently
expressed.
The draft loss due to sudden contraction of an area (he) is given by the
equation :
C= A*9B0WC
where
JTC — coefficient of sudden contraction based on —-, the ratio of the areas of the
smaller to the larger section = 0.5 { 1 — —r- j
As = area of the smaller section.
When the flue or passage through which the gases flow is suddenly
contracted, a considerable portion of the static head in the larger section
is converted into velocity head and a draft loss of some consequence, par-
ticularly in a short breeching, takes place. A sudden contraction should
always be avoided where possible. At times, however, due to obstruc-
tions or limited head-room, it is necessary to alter the size of the breeching,
but a sudden contraction may be avoided by gradually decreasing the
area over a length of several feet.
The draft loss due to a sudden enlargement of an area (ho) is given by the
equation :
where
K0 = coefficient of sudden enlargement based on -^, the ratio of the areas of the
small
ter to the larger section = f 1 - -p J
When the flue or passage through which the gases flow is suddenly
enlarged, a portion of the velocity head is converted into static head in the
larger section and, like the loss due to sudden contraction, a loss of some
consequence, particularly in short breechings, takes place. A sudden
enlargement in a breeching may be avoided by gradually increasing the
area over a length of several feet. In large masonry chimneys, the area of
the flue at the region of the breeching entrance is considerably larger
than the area of the breeching at the chimney, and a sudden enlargement
exists.
The draft loss through the economizer (&E) should be obtained from the
manufacturer but for general purposes it may be computed from the
following general equation :
ft. = 'c (31)
10*
194
CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS
where
Wn = pounds of gases flowing per hour per linear foot of pipe in each economizer
section.
N — number of economizer sections.
An economizer in a steam plant affects the draft in two ways, (1) it
offers a resistance to the flow of gases, and (2) it lowers the average
chimney gas temperature, thereby decreasing the available intensity. In
the case of a natural draft installation, both of these factors result in a
relative increase in the height of the chimney and, in the case of a large
plant, they may add as much as 20 or 30 ft to the height. The decrease
in the temperature of the gases after they have passed through the
economizer has an extremely important effect on the performance of a
natural draft chimney and also upon the performance of a fan.
CpNSTHUCTION DETAILS
For general data on the construction of chimneys reference should be
made to the Standard Ordinance for Chimney Construction of the
National Board of Fire Underwriters. Briefly summarized, these provisions
are as follows for heating boilers and furnaces:
The construction, location, height and area of the chimney to which a heating boiler
or warm-air furnace is connected affect the operation of the entire heating system. Most
residence chimneys are built of brick and may be either lined or unlined, but in either
case the walls must be air-tight and there should be only one smoke opening into the
chimney. Cleanout, if provided, must be absolutely air-tight when closed.
The walls of brick chimneys shall be not less than 3% in. thick (width of a standard
size brick) and shall be lined with fire-clay flue lining. Fire-clay flue linings shall be
manufactured from suitable refractory clay, either natural or compounded, and shall
be adapted to withstand high temperatures and the action of flue gases. They shall be
of standard commercial thickness, but not less than % in. All fire-clay flue linings shall
meet the standard specification of the Eastern Clay Products Association. The flue
sections shall be set in special mortar, and shall have the joints struck smooth on the
inside. The masonry shall be built around each section of lining as it is placed, and all
spaces between masonry and linings shall be completely filled with mortar. No broken
flue lining shall be used. Flue lining shall start at least 4 in. below the bottom of smoke-
pipe intakes of flues, and shall be continued the entire heights of the^flues and project
at least 4 in. above the chimney top to allow for a 2 in. projection of lining. The wash or
splay shall be formed of a rich cement mortar. To improve the draft the wash surface
should be concave wherever practical.
Flue lining may be omitted in brick chimneys, provided the walls of the chimneys
are not less than 8 in. thick, and that the inner course shall be a refractory clay brick.
All brickwork shall be laid in spread mortar, with all joints push-filled. Exposed joints
both inside and outside shall be struck smooth. No plaster lining shall be permitted.
Chimneys shall extend at least 3 ft above flat roofs and 2 ft above the ridges of peak
roofs when such flat roofs or peaks are within 30 ft of the chimney. The chimney
shall be high enough so that the wind from any direction shall not stnke the top of the
chimney from an angle above the horizontal. The chimney shall be properly capped with
stone, terra cotta, concrete, cast-iron, or other approved material; but no such cap
or coping shall decrease the flue area.
There shall be but one connection to the flue to which the boiler or furnace smoke-
pipe is attached. The boiler or furnace smoke-pipe shall be thoroughly grouted into the
chimney and shall not project beyond the inner surface of the flue lining.
The size or area of flue lining or of brick flue for warm-air furnaces depends on height
of chimney and capacity of heating system. For chimneys not less than 35 ft in height
above grate line, the net internal dimensions of lining should be at least 7 x 11 H in.
195
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
for a total leader pipe area up to 790 sq in. Above 790 and up to 1,000 sq in. of leader
pipe area the lining should be at least 11^ x 11 % in. inside. In case of brick flues not
less than 35 ft in height with no linings, the internal dimensions should be at least
8 x 12 in. up to 790 sq in. of leader area, and at least 12 x 12 in. for leader capacities up to
1,000 sq in. Chimneys under 35 ft in height are unsatisfactory in operation and hence
should be avoided.
CHIMNEYS FOR GAS HEATING
The burning of gas differs from the burning of coal in that the force
which supplies the air for combustion of the gas comes largely from the
pressure of the gas in the supply pipe, whereas air is supplied to a bed of
burning coal by the force of the chimney draft. If, with a coal-burning
boiler, the draft is poor, or if the chimney is stopped, the fire is smothered
and the combustion rate reduced. In a gas boiler or furnace such a
condition would interfere with the combustion of the gas, but the gas
would continue to pass to the burners and the resulting incomplete com-
bustion would produce a dangerous condition. In order to prevent incom-
plete combustion from insufficient draft, all gas-fired boilers and furnaces
should have a back-draft diverter in the flue connection to the chimney.
TABLE 2. SUGGESTED GENERAL DIMENSIONS FOR VERTICAL BACK-DRAFT DIVERTER
Table of Dimensions (In.)
PIPE
SIZE
A
B
C
D
E
P
G
H
I
J
K
L
M
3
3
3
5.5
7.0
3.8
0.7
4.4
3.0
1.5
2.5
0.7
1.5
2.3
4
4
4
7.2
9.5
5.0
1.0
6.0
4.0
2.0
3.5
1.0
2.0
3.0
5
5
5
9.4
10.8
5.3
1.5
8.0
5.0
2.3
4.0
0.9
2.4
3.5
6
6
6
11.5
12.0
5.6
1.9
9.8
6.0
2.5
4.5
0.8
2.7
4.0
7
7
7
13.5
13.9
6.4
2.3
11.6
7.0
2.9
5.3
0.9
3.1
4.6
8
8
8
15.5
15.8
7.1
2.7
13.4
8.0
3.2
6.0
1.0
3.5
5.3
9
9
9
17.5
17.5
7.7
3.1
15.2
9.0
3.5
6.7
1.0
4.0
5.8
10
10
10
19.7
18.8
7.9
3.6
17.2
10.0
3.8
7.3
1.0
4.3
6.2
11
11
11
22.2
20.7
8.4
4.3
19.6
11.0
4.1
8.0
1.5
4.6
6.6
12
12
12
24.7
22.2
8.7
5.0
22.0
12.0
4.4
8.5
1.7
5.0
7,0
196
CHAPTER 10. CHIMNEYS AND DRAFT CALCUIATIONS
A study of a typical back-draft diverter shows that partial or complete
chimney stoppage^will merely cause some of the products of combustion
to be vented out into the boiler room, but will not interfere with com-
bustion^ In fact, gas-designed appliances must perform safely under such
a condition to be approved by the American Gas Association Laboratory.
Other functions of the back-draft diverter are to protect the burner and
pilot from the effects of down-drafts, and to neutralize the effects of
variable chimney drafts, thus maintaining the appliance efficiency at a
substantially constant value. Converted boilers or furnaces, as well as
gas-designed appliances, should be provided with back-draft diverters.
Since back-draft diverters have a special function to perform in pro-
tecting gas burning appliances, it is necessary that they should be built
to the proper size as shown in Table 2 for a vertical type and in Table 3
for a horizontal arrangement. Equipment of this kind listed by the
American Gas Association Testing Laboratory must bear the listing
symbol A.G.A.
. SUG
GESTED GENERAL DIMENSIONS FOR HORIZONTAL BACK-DRAFT DIVERTER
t
, r ,._ tei n
1
[
i
)
r"
~i
^ /-Baffle
1 / /
r
^
E
E
3
(
• — 1-\- — 1
L
Baffle
^ \
Baffle
strap
nlet
-Relief opening *^
Table of Dimensions (In.)
PIPE
SIZE
A
B
C
D
E
F
G
H
I
J
E
L
M
3
3
3
6
1.5
4.8
3.8
1.4
2.5
2,5
2.5
2.1
0 6
1.8
4
4
4
8
2.0
4.8
5.0
1.9
3.4
3.4
3.4
2.9
0.8
2.3
5
5
5
10
2.5
4.8
6.3
2.4
4.2
4.2
4.2
3.5
0.9
2.9
6
6
6
12
3.0
4.8
7.5
2.9
5.0
5.0
5.0
4.3
1.1
3.5
7
7
7
14
3.5
4.8
8.8
3.4
5.9
5.9
5.9
5.0
1.3
4.1
8
8
8
16
4.0
4.8
10.0
3.9
6.7
6.7
6.7
5.6
1.5
4.7
9
9
9
18
4.5
4.8
11.3
4.4
7.5
7.5
7.5
6.4
1.7
5.3
10
10
10
20
5.0
4.8
12.5
4.9
8.4
8.4
8.4
7.0
1.9
5.8
11
11
11
22
5.5
4.8
13.8
5.4
9.2
9.2
9.2
7.8
2.1
6.4
12
12
12
24
6.0
4.8
15.0
5.9
10.0
10.0
10.0
8.5
2.3
7.0
197
HEATING VENTIUITING AIR CONDITIONING GUIDE 1938
As is the case with the complete combustion of almost all fuels, the
products of combustion for gas are carbon dioxide (C09) and water vapor
with just a trace of sulphur tripxide (503). Sulphur usually burns to the
trioxide in the presence of an iron oxide catalyst. The volume of water
vapor in the flue products is about twice the volume of the carbon dioxide
when coke oven or natural gas is burned. Because of the large quantity
of water vapor which is formed by the burning of gas, it is quite important
that all gas-fired central heating plants be connected to a chimney having
a good draf t.^ Lack of chimney draft causes stagnation of the products of
combustion in the chimney and results in the condensation of a large
amount of the water vapor. A good chimney draft draws air into the
chimney through the openings in the back-draft diverter, lowers the dew
point of the mixture, and reduces the tendency of the water vapor to
condense.
The flue connections from a gas-fired boiler or furnace to the chimney
should be of a non-corrosive material. In localities where the price of
TABLE 4. MINIMUM ROUND CHIMNEY DIAMETERS FOR GAS APPLIANCES (INCHES)
HJCIOHT or
GAS CONSUMPTION m THOUSANDS OF Bin PER HOTJB
FZZT
100
200
300
400
500
750
1000
1500
2000
20
4.50
5.70
6.60
7.30
8.00
9.40
10.50
12.35
13.85
40
4.25
5.50
6.40
7.10
7.80
9.15
10.25
12.10
13.55
60
4.10
5.35
6.20
6.90
7.60
8.90
10.00
11.85
13.25
80
4.00
5.20
6.00
6.70
7.35
8.65
9.75
11.50
12.85
100
3.90
5.00
5.90
6.50
7.20
8.40
9.40
11.00
12.40
gas requires the use of highly efficient appliances, the material used for
the flue connection not only should be resistant to the corrosion of water,
but should resist the corrosion of dilute solutions of sulphur trioxide in
water. Local practice should be followed in the selection of the most
appropriate flue materials.
When condensation in a chimney proves troublesome, it may be
necessary to provide a drain to a dry well or sewer. The cause of the
excessive condensation should be investigated and remedied if possible.
This may be done by raising the flue temperature slightly or increasing
the size of the back-draft diverten The protection of unlined chimneys
has been investigated and the results indicate that after the loose material
has been removed, the spraying with a water emulsion of asphalt-
chromate provides an excellent protection,
A chimney for a gas-fired boiler or furnace should be constructed in
accordance with the principles applicable to other boilers. Where the
wall forming a smoke flue is made up of less than an 8-in. thickness of
brick, concrete, or stone, a burnt fire-day flue tile lining should be used.
Care^ should be used that the lengths of flue tile meet properly with no
openings at the joints. Cement mortar should be used for the entire
chimney.
Table 4 gives the minimum cross-sectional diameters of round chim-
198
CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS
neys (in inches) for various^ amounts of heat supplied to the appliance,
and for various chimney heights. This is in accordance with American
Gas Association recommendations.
PROBLEMS IN PRACTICE
1 • What are the principle factors influencing the intensity of natural draft?
The intensity of natural draft depends largely upon the height of chimney above the
grate bar level and the temperature difference between the chimney gases and the
atmosphere.
2 • What two kinds of draft need he considered?
Natural draft caused by temperature differences, and artificial draft caused by me-
chanical forcing.
3 • What is the effective height of a chimney?
The height from the grate level to the top of the chimney is the effective height in pro-
ducing natural draft.
4 • What dual purpose does a tall chimney fulfill?
A tall chimney primarily creates the necessary draft to move the air required for the
combustion process and to move the products of combustion, and secondarily it dis-
charges the gases at a high elevation to prevent them from becoming a nuisance.
5 • What is the direct influence of the height on the design of a chimney?
The immediate purpose of height is to provide that draft intensity under the conditions
of chimney gas temperature such that it will be adequate to overcome all the frictional
resistances of the installation, as well as to provide for the actual gas movement.
6 • Of what importance is chimney cross-sectional area in stack design?
The area should be as large as is economically feasible in order that the frictional loss
for the chimney he
in overcoming the i
for the chimney height should not destroy the effectiveness of the height-created draft
he necessary frictional resistances of the boiler and its flue connections.
7 • Of what importance is the Reynolds number in chimney design?
It permits the selection of a more specific value of the chimney friction factor, rather
than a general one, to correspond with conditions of size, nature of the gas, rate of gas
flow, and condition of the surface.
8 • a. Name the principle advantages of natural draft.
b. Name the principle disadvantages of natural draft.
a. Simplicity, reliability, freedom from mechanical parts, low cost of maintenance,
relatively long life, relatively low depreciation, operation with no power requirement.
b. Lack of flexibility, irregularity, dependence on surroundings, susceptibility to tem-
perature changes.
9 • How is mechanical draft created?
By forced draft, by induced-draft fans, or by a Venturi chimney.
10 • Distinguish between theoretical and available draft.
Theoretical draft is the difference in pressure inside and outside the base of a chimney
when it is under operating temperatures but when there are no gases flowing. Available
draft is less than theoretical draft by the friction loss due to the flow of gases through
the chimney.
199
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
11 • Explain the term efficiency of a natural draft chimney.
The efficiency of a chimney is the ratio of the work it does in moving gases to the theo-
retical amount of power it generates.
12 • How is the available draft used in a heating plant?
The available draft at the base of the chimney is used to overcome the loss in pressure
through the grate, the fuel bed, the boiler passes, the breeching.
13 • What are some of the factors that influence the draft loss through the fuel
bed?
Uniformity and size of coal, the amount of ash mixed with the fuel on the grate, thickness
of fuel bed, rate of combustion, amount of air supply as related to the coal burning rate.
14 • How does the volatile matter content affect the draft loss through the fuel
bed?
The higher the volatile content and the lower the fixed carbon content, the lower the
draft loss.
15 • In what cases will there he no fuel bed draft loss?
In oil, gas, and powdered fuel firing the fuel is mixed and burned in suspension; con-
sequently, no measurable resistance is encountered in the combustion zone.
16 • Is it possible to state an average value for the draft loss through a boiler
and its setting?
No. The draft loss varies widely and depends on many factors such as the size and type
of gas passageways. The manufacturer is usually able to supply such information.
17 • Of what significance is the CDs content of stack gases in establishing
draft loss?
The COz content of the exit gases is a measure of the completeness of the combustion and
the amount of excess air supplied. Low COj indicates a high excess of air and hence
a high draft loss.
18 • What two effects does an economizer have on the draft loss?
An economizer offers resistance to the flow of gases over the added surfaces; it lowers the
temperature of the gases going to the chimney and therefore decreases the available
draft. This decrease often necessitates the addition of forced draft.
19 • What main provisions should be considered in good chimney construction?
Chimneys should be air-tight and connected to only one smoke opening. The chimney
top should be high enough above surroundings so the wind will not strike it at any angle
above the horizontal. ^ Chimney walls should be not less than one brick in width, and
they should be lined with fire-clay tile of the size required for the attached heating unit.
Tile lining sizes are stated as outside dimensions; therefore, their effective dimensions
are less by the thickness of the wall.
20 • What is the purpose of a back draft diverter as used on gas burning units?
Since the fuel is supplied under pressure independent of draft it is necessary to free the
unit from the variable chimney draft and to supply air for combustion in direct propor-
tion to the supply of fuel gas. The back draft diverter protects the pilot and burners
from down drafts.
200
Chapter 11
AUTOMATIC FUEL BURNING EQUIPMENT
Classification of Stokers, Combustion Process and Adjustments,
Furnace Design, Classification of Oil Burners, Combustion
Chamber Design, Classification of Gas-Fired Appliances
A UTOMATIC mechanical equipment for the combustion of solid,
f\ liquid and gaseous fuels is considered in this chapter.
MECHANICAL STOKERS
A mechanical stoker is a device that feeds a solid fuel into a combustion
chamber, provides a supply of air for burning the fuel under automatic
control and, in some cases, incorporates a means of removing the ash and
refuse of combustion automatically. Coal can be burned more efficiently
by a mechanical stoker than by hand firing because the stoker provides a
uniform rate of fuel feed, better distribution in the fuel bed and positive
control of the air supplied for combustion.
Stokers may be divided into four types according to their construction,
namely, (1) overfeed flat grate, (2) overfeed inclined grate, (3) underfeed
side cleaning type, and (4) underfeed rear cleaning type.
Overfeed Flat Grate Stokers
This type is represented by the various chain- or traveling-grate stokers.
These stokers receive fuel at the front of the grate in a layer of uniform
thickness and move it back horizontally to the rear of the furnace. Air is
supplied under the moving grate to carry on combustion at a sufficient
•rate to complete the burning of the coal near the rear of the furnace.
The ash is carried over the back end of the stoker into an ashpit beneath.
This type of stoker is suitable for small sizes of anthracite or coke breeze
and also for bituminous coals, the characteristics of which make it
desirable to bum the fuel without disturbing it. This type of stoker
requires an arch, over the front of the stoker to maintain ignition of the
incoming fuel. Frequently, a rear combustion arch is required to main-
tain ignition until the fuel is fully consumed. A typical traveling-grate
stoker is illustrated in Fig. 1.
Another and distinct type of overfeed flat-grate stoker is the
spreader (Fig., 2) or sprinkler type in which coal is distributed either
mechanically or by air over the entire grate surface. This type of stoker
has a wide application on small sized fuels and on certain special fuels
such as lignites, high-ash coals, and coke breeze.
201
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Overfeed Inclined Grate Stokers
In general the combustion principle is similar to the flat grate stoker,
but this stoker (Fig. 3) is provided with rocking grates set on an incline to
advance the fuel during combustion. Also this type is provided with an
ash plate where ash is accumulated and from which it is dumped periodi-
cally. This type of stoker is suitable for all types of coking fuels but
preferably for those of low volatile content. Its grate action has the
tendency to keep the fuel bed well broken up thereby allowing for free
I I I T T
FIG. 1. OVERFEED TRAVELING-GRATE STOKER
Coal conveying pipe
^—
Burner nozzle
FIG. 2. SPREADER STOKER-PNEUMATIC TYPE
passage of air. Because of its agitating effect on the fuel it is not so
desirable for badly clinkering coals. Furthermore, it should usually be
provided with a front arch to care for the volatile gases.
Underfeed Side Cleaning Stokers
In this type (Fig. 4), the fuel is introduced at the front of the furnace to
one or more retorts, is advanced away from the retort as combustion
progresses, while finally the ash is disposed of at the sides. This type of
stoker is suitable for all coking coals while in the smaller sizes it is suitable
for small sizes of anthracites. In this type of stoker the fuel is delivered
to a retort beneath the fire and is raised into the fire. During this process
202
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
the volatile gases are released, are mixed with air, and pass through the
fire where they are burned. The ash may be continuously discharged as
in the small stoker or may be accumulated on a dump plate and periodi-
cally discharged. This stoker requires no arch as it automatically pro-
vides for the combustion of the volatile gases.
Secondary-
I fof — Ignited and partuHy coked fuel
FIG. 3. OVERFEED INCLINED GRATE STOKER
FIG. 4. UNDERFEED PLUNGER TYPE STOKER
Underfeed Rear Cleaning Stokers
This type of stoker accomplishes combustion in much the same manner
as the side cleaning type, but consists of several retorts placed side by side
and filling up the furnace width, while the ash disposal is at the rear. In
principle, its operation is the same as the side cleaning underfeed.
203
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Stokers also may be classified according to their size based upon coal
feed rates. The following classification has been made by the United
States Department of Commerce in cooperation with the Stoker Manu-
facturers' Association'.
Class 1. Up to and including 60 Ib of coal per hour.
Class 2. 60 to 100 Ib of coal per hour.
Class 3. 100 to 300 Ib of coal per hour.
Class 4. 300 to 1200 Ib of coal per hour.
(A fifth class is included covering stokers having a feeding capacity above 1200 Ib
of coal per hour).
Class 1 and Class 2 Stokers, Household
Since these stokers are used primarily for home heating, it is desirable
that their design be simple and attractive in appearance, and that they be
quiet and automatic in .operation.
A common type of stoker in this class consists, essentially of a coal
reservoir or hopper, a screw for conveying the fuel from the hopper to the
burner head or retort; a fan which supplies the air for combustion, a
FIG. 5. UNDERFEED SCREW STOKER, HOPPER TYPE
transmission for driving the coal feed worm, and an electric motor or
motors for supplying the motive power for both coal feed and air supply
as indicated in Fig. 5. The shape of the retort in this class of stokers is
usually round although rectangular retorts are favored by some manu-
facturers. In all cases, however, the retort incorporates tuyeres through
which the air for combustion is admitted.
Some household stokers are provided with an automatic grate-shaking
mechanism together with screw conveyors for removing the ash from the
ashpit (Fig. 6) and depositing it in an ash receptacle outside the boiler.
Certain types can also be provided with a coal conveyor which takes
coal from the storage bin and maintains a full hopper at the stoker. In
some cases the coal bin functions as the stoker hopper as shown in Fig. 7,
and an extended worm is used to convey the fuel to the combustion furnace.
. Domestic stokers may feed coal to the furnace either intermittently or
with a continuous flow regulated automatically to suit conditions.
Household stokers are made for ail classes of fuel ^anthracite, bitu-
minous and semi-bituminous coals, and coke. The United States Depart-
204
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
went of Commerce has issued commercial standards for household anthra-
cite burners, which may be obtained by application. Standards of
performance for bituminous coal stokers are also being developed by
Bituminous Coal Research, Inc. The standards for anthracite stokers are
described in the next paragraphs.
Operating Requirements for Anthracite Stokers
Efficiency. The over-all efficiency of the unit at all points above 50 per cent of maxi-
mum coal feed shall be above 50 per cent when installed in a round sectional cast-iron
boiler having three intermediate sections and 1H in. of asbestos insulation or its equiva-
FIG. 6. UNDERFEED SCREW STOKER WITH AUTOMATIC ASH REMOVAL
0 tf
FIG. 7. UNDERFEED SCREW STOKER, BIN FEED TYPE
lent in good condition of repair, operating at 50 per cent or more of the boiler capacity.
The efficiency shall be maintained for any continuous period of 4 hours during any test
or observation run.
Ash Loss. Combustible in ash shall not exceed 7.5 per cent of the Btu content of the
coal as fired at any rate of coal feed above 50 per cent of maximum. Methods of test
according to Code No. 3 of the A.S.H.V.E.1 are to be followed in all details applicable
to stoker testing.
Clinker. Ash removing systems should at all times be capable of disposing of any
clinker which may be formed under any conditions of operation with the coals prescribed.
*A..S.H.V.E. Performance Test Code for Steam Heating Solid Fuel Boilers (Code 3), (A.S.H.V.E.
TRANSACTIONS, Vol. 35, 1929, p. 332).
205
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Combustion Rate. A combustion rate of at least 13 Ib per square foot of horizontal
projected area of ash ring per hour must be continuously maintained for at least 9 hours
with the above conditions of efficiency, ash and clinker.
Flue Gas. Flue gas shall be not below 6 per cent in carbon dioxide with a reasonably
tight boiler at any rate of operation above 50 per cent of maximum coal feed.
Maximum Rating^ The maximum rating, in terms of gross square feet of water or
steam radiation which the burner will supply, when intended for installation in the
average existing cast-iron boiler, shall be 90 per cent of the maximum steam produced in
a round cast-iron boiler in good repair having three intermediate sections and the
equivalent of 1J£ in. of asbestos insulation. However, in no case shall the maximum
rating be greater than 29 sq ft of direct steam radiation for each pound of coal fired per
hour, and in no case shall ratings be based upon efficiency figures below 50 per cent.
The maximum rating as defined in the preceding paragraph shall be based upon com-
bustion of Pennsylvania anthracite having the following approximate analysis:
Volatile matter 3.5 to 9 per cent ; ash content not to exceed 15 per cent ; sulphur content
under 1.5 per cent; ash fusing temperature 2750 F, or above (volatile, ash and sulphur
content on dry basis in accordance with A.S.T.M. method D271-33) ; Btu content 12,000
or above; properly sized as follows: A No. 1 buckwheat should pass through a round
mesh screen having %6 in- holes and over a similar screen having 5ie m- holes. The
undersizing should not exceed 15 per cent and the oversizing should not exceed 10 per
cent. A No. 2 buckwheat (rice) should pass through a round mesh screen having holes
5ie in. in diameter and over a like screen having holes of %e in. in diameter. The under-
sizing should not exceed 15 per cent and the oversizing should not exceed 10 per cent.
Coal Storage. It is recommended that the coal bin or closet be constructed so as to
be dustproof.
Electrical Consumption. The electrical consumption shall not exceed 18 kwh per
2000 Ib of coal burned at any rate of coal feed above 50 per cent of the maximum.
Operation Upon Other Sizes of Coal. The foregoing specifications have been drafted
for operating with the Nos. 1 and 2 buckwheat sizes of anthracite. In the event that
other sizes are recommended, ratings shall be based upon the same efficiency and ash
loss requirements.
Banking. The burner shall be so constructed or controlled as to maintain a fire
during an indefinite banking period.
Acceleration. When the burner resumes operation after a 12 hour banking period, the
time required for the stack temperature to reach a normal maximum shall not exceed
60 min.
Stoker-Fired Units
Boilers and air conditioners especially designed for stokers are now
becoming available. Present designs feature better coordination between
the heat absorber and the stoker. Increased setting height and furnace
volume and more heating surface than in conversion installations are
usually to be found in these stoker units.
Class 3 Stokers, Apartment House, Small Commercial
This class is used extensively for heating plants in apartments and
hotels, and also for small industrial plants such as laundries, bakeries, and
creameries. The majority of stokers used in this field are of the underfeed
type. The principal exception is an overfeed type having step action
grates in a horizontal plane and so arranged that they are alternately
moving and stationary, and are designed to advance the fuel during com-
bustion to an ash plate at the rear.
All of the stokers are provided with a coal hopper outside of the boiler.
In the underfeed types, the coal feed from this hopper to the furnace may
be accomplished by a continuously revolving screw or by an intermittent
206
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
plunger. The drive for the coal feed may be an electric motor, or a steam
or hydraulic cylinder. With an electric motor, the connection between
the driver and the coal feed may be through a variable speed gear train
which provides two or more speeds for the coal feed; or it may be through
a simple gear train and a variable speed driver for the change in speed of
the coal feed; or a simple gear train with a coal feed having an adjustment
for varying the travel of the feeding device. With a steam or hydraulic
cylinder, the power piston is connected directly to the coal feeding
plunger.
The stokers in this class vary also in their retort design according to the
fuels and load conditions. The retort is placed approximately in the
middle of the furnace and is provided with tuyere openings at the top on
all sides. In the plunger-feed type the retort extends from the inside of
the front wall entirely to the rear wall or to within a short distance of the
rear wall. This type of retort has tuyeres on the sides and at the rear.
These stokers also differ in the grate surface surrounding the retort.
In many of the worm-feed stokers this grate is entirely a dead plate on
which the fuel rests while combustion is completed. In the dead-plate
type, all of the air for combustion is furnished by the tuyeres at the retort.
Because of this, combustion is well advanced over the retort so that it
may easily be completed by the air which percolates through the fuel bed.
With the dead-plate type of grate the ash is removed through the fire
doors and it is therefore desirable that the fuel used shall be one in which
the ash is readily reduced to a clinker at the furnace temperature, in
order that it may be removed with the least disturbance of the fuel bed.
In other stokers in this class, the grates outside of the retort are air-
admitting and some stokers have shaking grates. These grates permit a
large part of the ash to be shaken into the ashpit beneath, while the
clinkers are removed through the fire doors. With this type of grate, the
main air chamber extends only under the retort while the side grates
receive air by natural draft from the ashpit.
In still other stokers of this class, the main air chamber extends beyond
the retort and is covered with fuel-bearing, air-supplying grates. With
this type of grate, the fuel is supplied with air from the main air chamber
throughout combustion. Also with this type of grate, dump plates are
provided beyond the grates where the ash accumulates and from which it
can be dropped periodically into the ashpit beneath.
Stokers in this class are compactly built in order that they may fit into
standard heating boilers and still leave room for sufficient combustion
space above the grates. The height of the grate is approximately the same
as that of the ordinary grates of boilers, so that it is usually possible to
install such stokers with but minor changes in the existing equipment.
In some districts, there are statutory regulations governing such settings.
These stokers vary in furnace dimensions from 30 in. square to approxi-
mately 66 in. square. The capacity of the stokers is measured by the
amount of coal that can be burned per hour. In general, manufacturers
recommend that, for continuous operation, the coal burning rate shall not
exceed 25 Ib of coal per square foot of grate per hour, while for short
peaks this rate may be increased to 30 Ib per hour. Although these
stokers were designed to burn bituminous coal, types are available for
207
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
the semi-bituminous coals such as Pocahontas and New River. They can
also be used to burn the small sizes of anthracite but at a somewhat
lower rate.
Class 4 Stokers, Medium Commerial
These stokers are usually of the screw feed type without auxiliary
plungers or other means of distributing the coal. Rectangular retorts
with sectional tuyeres and dead plates without air ports are employed.
The unit type of construction is almost universally used, the unit incor-
porating the hopper, the transmission for driving the feed screw, and the
fan for supplying air for combustion.
Class 4 Stokers, Large Commercial, Small High Pressure Plants
Stokers in this group vary widely in details of mechanical design and
the several methods of feeding coal previously described may be employed
Such methods of applying power to the fuel conveying mechanism as,
continuous gear train transmission, ratchet type speed reducer, hydraulic
cylinder and steam cylinder are used. Varying methods of ash disposal
are found in this class.
Large Stokers
This class includes stokers with hourly burning rates of over 1200 Ib
of coal per hour. The prevalent stokers in this field are :
a. Overfeed flat grate stokers.
b. Overfeed inclined grate stokers.
c. Underfeed side cleaning stokers.
d. Underfeed rear cleaning stokers.
Overfeed inclined grate stokers are seldom built in sizes of over 500 hp
and are not as extensively used as other types of stokers.
Underfeed side cleaning stokers are made in sizes up to approximately
500 hp and in this field are extensively used. These stokers are not so
varied in design as those in the smaller classes although the principle is
much the same. Practically all of them are of the front coal feed type,
either power driven or steam driven. Dump plates at the side are
manually operated. These stokers are heavily built and designed to
operate continuously at high boiler ratings with a minimum amount of
attention. Because of the fact that all volatile gases must pass through the
fire before reaching the combustion chamber, these stokers will operate
smokelessly under ordinary conditions. Also because of the fact that
these stokers are always provided with forced draft, they are the most
desirable type for fluctuating loads or high boiler ratings.
' In the design of the grates for supporting the fuel between the retort
and the ash plates, the stokers differ in providing for movement of the
fuel during combustion. Some stokers are designed with fixed grates of
sufficient angle to provide for this movement as the bed is agitated by the
incoming fuel, while others have alternate moving and stationary bars in
this area and provide for this movement mechanically. In either type,
with 'proper operation, all refuse will be deposited at the dump plate.
208
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
Recent developments in this type of stoker provide for sliding distributor
blocks along the bottom of the retorts which give flexibility in providing
proper distribution of fuel over the grate area and assist in preventing
coke masses when strong coking coals are used. Another difference in
these stokers is that some use a single air chamber under the whole grate
area thus having the same air pressure under the ignition area as under
the rest of the grate, while others have a divided air chamber using the
full air pressure under the ignition area and a reduced air pressure under
the remainder of the grate. These stokers vary in size from approxi-
mately 5 sq ft to a maximum of 8% sq ft.
The most prevalent type of rear cleaning underfeed stoker is the
multiple retort design. Occasionally double or triple retort side cleaning
underfeeds are made. The multiple retort underfeed stoker is made for
the largest sizes of boilers for large industrial plants and central stations.
This stoker has reached a very fine stage of development mechanically
and in the matter of air supply and control. In some instances zoned air
control has been applied both longitudinally and transversely to the grate
surface. Ash dumps on smaller sizes are sometimes manually operated.
The Combustion Process
Due to the marked differences in design and operating characteristics
of stokers and the widely differing characteristics of stoker fuels, it is
difficult to generalize on the subject of combustion in automatic stokers.
In anthracite stokers, which are almost exclusively of the small (Class 1)
underfeed type, burning takes place within the stoker retort. The ash
and refuse of combustion spills over the edge of the retort into an ashpit
or receptacle from which it may be removed either manually or auto-
matically. Anthracite is usually supplied for stoker firing in No. 1
buckwheat or No. 2 buckwheat size. Those stokers burning coke operate
in a similar manner to anthracite stokers.
Since the majority of bituminous coal stokers used in heating plants
operate on the underfeed principle some general observations of their
operation are given.
When the coal is fed from the hopper or bin into the retort it is generally
degraded to some extent and some segregation of sizes occurs. Because
of these factors there may be some difference in the actions occurring in the
various portions of the retort.
The coal moving upward in the retort toward the zone of combustion
established by previous kindling of the fire is heated by conduction and
radiation from the zone of combustion. As the temperature of the coal
rises it first gives off moisture and occluded gases, which are largely
non-combustible. When the temperature increases to around 700 or
800 F, the coal particles become plastic, the degree of plasticity varying
with the type of coal.
A rapid evolution of combustible volatile matter occurs during and
directly after the plastic stage of the coal. The distillation of volatile
matter continues above the plastic zone and the coal is coked. The
strength and porosity of the coke formed will vary according to the size
and characteristics of the coal used.
209
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
As more coal is fed from below the mass of coke continues to grow
forming a coke tree, plug or spar as it is variously designated. After a
period of time, dependent upon the strength of the coke formed, pieces of
the coke tree break off and fall upon the hearth surrounding the retort
or within the retort itself where they are burned.
While part of the ash fuses into particles at the surface of the coke as it
is released, most of it is freed in unfused flakes or grains. The greater
part of this unfused ash remains on the hearth or dead plates although a
part may be expelled from the furnace with the gases.
The ash layer becomes thicker with time and that near the retort, being
exposed to temperatures which are high enough at times, fuses into a
clinker. The temperature attained in the fuel bed, the chemical compo-
sition and homogeneity of the ash, and the time of heating are factors
which govern the degree of fusion.
FIG. 8. CROSS-SECTION OF FUEL BED
WITH WEAKLY COKING COAL
FIG. 9. CROSS-SECTION OF FUEL BED
WITH STRONGLY COKING COAL
Bituminous coal stokers of the Class 1 type operate on the principle
of the removal of ash as clinker and clinker tongs are provided to facilitate
this purpose. Typical representations of underfeed bituminous stoker
fuel beds are shown in Figs. 8 and 9.
The appearance of such fuel beds is very ragged at times, and large
masses of coke build up, surrounded by blowholes with intense white
flame indicating the presence of excess air. There is a natural tendency
for users to disturb the fuel bed and make it conform to the conventional
representation or ideal fuel bed. Such attention should not be required,
as usually the fuel bed tends to correct its own faults as the cycles of
plasticity, coke tree formation and ash fusion recur.
There are a number of factors which materially affect the rate and type
of ^ combustion obtained in stoker usage, the most important of these
being: the type and design of stoker, the type and characteristics of the
fuel, the method of stoker installation and the method of stoker operation.
210
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
Furnace Design
The burning of the fuel on the grate or in the retort will be influenced
directly by the stoker design. The burning of the volatile gases above the
fuel bed is a matter of furnace design. Proper care should be taken to
provide furnaces sufficiently liberal in volume and with the grates or
retorts at a sufficient distance from the heating surface to permit proper
combustion of the gases. Smoke and low efficiency will result if the
furnace is too small to permit proper mixing of the gases and completion
of combustion.
TABLE 1. RECOMMENDED SETTING HEIGHTS FOR HEATING BOILERS
EQUIPPED WITH MECHANICAL STOKERS'*
FIREBOX BOIUCBS
Actual Loadb
2500
5000
7500
10000
12500
15000
20000 |
25000
30000
A 18"
18'
20"
20"
22"
22"
24" !
24"
24"
B
42"
48"
54"
60"
66"
72"
78" ;
84"
84"
A — Distance from bottom of Water Leg to floor. B m Distance from Crown Sheet to bottom of Water Leg.
COMPACT WELDED BOILERS
Actual Loadb
2500 j 5000 i
7500
| 10000 '
12500
15000
20000
25000
30000
A
18"
18"
20"
i 20"
22"
22"
24" ' 24"
24"
B
30"
33" 1
!
36"
: 42" j
45"
48" 54"
60"
60"
A = Distance from bottom of Water Leg to floor. B = Distance from Crown Sheet to bottom of Water Leg.
H. R. T. BOILEBS
HP
50
75 | 100
125
150
i
175 i 200 i 225
250
1
275 300
A
5'-0"
5'-6" ! 6'-0"
6'-6"
7'-0"
7'-0" ; 7'-6" 8'-0"
8'-6"
9'-0" 9'-0"
A = Distance from bottom of shell to floor.
Hp - Installed horsepower.
In the case of the Firebox or Compact Welded type boilers the desired setting height can be obtained by
combining A and B dimensions. The load ratings shown for this class of boilers are actual developed loads
in square feet of equivalent cast-iron steam radiation and are not manufacturers' ratings.
The setting heights given for H. R. T. boilers may be used for developed loads up to 50 per cent above
normal rating.
•From Data prepared by the Midwest Stoker Association.
bExpressed as steam radiation, 1 sq ft = 240 Btu.
The standards that have been most universally adopted for the propor-
tioning of furnaces for bituminous coal stokers are those of the Midwest
Stoker Association and the Steel Heating Boiler Instittite. See Chapter 13.
Table 1 gives recommended setting heights for heating boilers equipped
with mechanical stokers using bituminous coal.
Furnace volume is not an important item in anthracite stoker instal-
lations. Due care should be exercised for both anthracite and bituminous
stokers to prevent intense heat application on the metal surfaces of the
combustion chamber. The installation of a baffle or adjustment in setting
height of the stoker may be desirable in some cases.
211
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
The prime essentials of good furnace design are: correct proportions,
moderate combustion rate, adequate furnace volume and sufficient flame
clearance. If these factors are properly compensated for and provision is
made for the proper mixing of the gases bituminous coal stokers will
operate smokelessly. In those stokers which are operated intermittently,
however, some smoke may be produced during the off periods.
Combustion Adjustments
Satisfactory stoker performance may be secured by regulating the coal
feed and the air supply so as to maintain, as nearly as possible, an ideal
balance between the load demand and the heat liberated by the fuel.
When the coal is consumed at about the same rate as that which it is fed
this balance exists and uniform fuel bed conditions will be found. Under
such conditions no manual attention to the fuel bed should be required
other than the removal of clinker in those stokers which operate on this
principle of ash removal.
Since complete combustion is not obtained in stoker furnaces receiving
only the air theoretically required, it is necessary, even under the best
of conditions, to supply from 30 to 50 per cent excess air to obtain desired
combustion results. Due to the variable characteristics of solid fuels in
burning, consideration must be given to a number of factors which affect
the maintenance of the combustion conditions wanted.
The specified rate of coal feed of a stoker may vary due to changes in
the bulk density of the coal dependent upon : (a) the size of coal, (6) dis-
tribution of size in the coal, (c) segregation of coal in the stoker hopper,
and (d) friability of the coal.
The following factors may affect the rate of air supply: (a) changes in
fuel bed conditions and resistance, (&) changes in furnace draft due to a
variety of causes, i.e., changes in chimney draft because of weather
changes, seasonal changes, back drafts, failure or inadequacy of auto-
matic draft regulator, use of chimney for other purposes, possible stoppage
of the chimney and changes in draft resistance of boiler due to partial
stoppage of the flues, and (c) changes in air inlet adjustments to the fan.
Many domestic bituminous stokers now incorporate some method of
automatic control which compensates for changes in fuel bed resistance.
Since a secondary source of air due to leakage is present in most installa-
tions, the use of an automatic draft regulator to maintain the furnace
draft at about 0.05 in. of water is desirable. This is quite important with
intermittently operated stokers. Some fuel is burned by natural draft in
the off periods, when fuel is not being fed, and it is essential that the
burning in these periods be controlled. With excessive draft, due either
to fan pressure or chimney pull, an increase in the discharge of soot and
fly ash from the combustion chamber will result.
Measurement of the Efficiency of Combustion
As efficient combustion is based upon a certain percentage of excess air,
it is possible to determine the results by analysis of the gases formed by
the combustion process. An Orsat apparatus can be used to determine the
percentage (by volume) of the carbon dioxide (C02), oxygen (02) and
212
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
carbon monoxide (CO) in the flue gases. Due to variations in the fuel bed
and rate of burning of stoker-fired .solid fuels it is not sufficient to analyze
a grab sample. A continuous gas sample drawn at a constant rate through-
out an operating period of reasonably long duration should be used.
A COz reading of 12.5 to 14 per cent indicates that the excess air
supplied is in the range of 30 to 50 per cent. The presence of CO indicates
a loss due to improper mixing of the air and the gases of combustion;
As an increase in excess air maintained during on periods will decrease the
tendency toward smoke in the off periods of intermittently operated
bituminous coal stokers, care should be taken that the delivery of air by
the fan is great enough to avoid smoke.
Controls
The industry developed by stokers in Classes 1, 2, 3 and 4 has been due
as much to the application of proper controls as to the stoker itself. This
is especially true of Class 1 stokers because of their application to resi-
dential heating, a field wherein the majority of owners and users are not
familiar with control problems or stoker operation.
The usual controls applied are as follows:
a. Thermostats (plain and clock).
b. Limit Controls (steam, vapor, vacuum, hot water, or air).
c. Stack Temperature or Time Controls (for actuating fires periodically).
d. Relay (for low voltage controls).
e. Safety or Overload Cutout (for protection against overload).
/. Low Water Cutout (steam, vapor and vacuum).
DOMESTIC OIL BURNERS
An oil burner is a mechanical device for producing heat automatically
and safely from liquid fuels. This heat is produced in the furnace or fire-
pot of hot water or steam boilers or warm air furnaces and is absorbed by
the boiler, and thus made available for distribution to the house through
the heating system.
With oil, as with any kind of fuel, efficient heat production requires that
all combustible matter in the fuel shall be completely consumed and that
it shall be done with a minimum of excess air. The combustion of oil is a
rather rapid chemical reaction. Excess air provides an over supply of
oxygen so that all of the oil, composed of carbon and hydrogen, will be
completely oxidized and thus produce all the heat possible. The use of
unreasonable quantities of air in excess of theoretical combustion require-
ments results in lowered efficiencies due to increased stack losses. Such
losses, if not accompanied by unburned products of combustion (saturated
and unsaturated hydrocarbons, hydrogen, etc.), may be offset somewhat
by increasing the secondary heating surfaces of the heat absorbing
medium, boiler or furnace.
Oil is a highly concentrated fuel composed mainly of hydrogen and
carbon. In its liquid form oil cannot burn. It must be converted into a
gas or vapor by some means. If the excess air ^is to be kept within
efficient limits it means that air must be supplied in carefully regulated
213
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
quantities. The air and oil vapor must be vigorously mixed to get a
rapid and complete chemical reaction. The better the mixing, the less
excess air that will be needed. The combustion must take place in a
space that maintains the temperatures high so the reaction will not be
stopped before completion. When equipped with a means of igniting the
oil and safety devices to guard against mishaps, the oil burner possesses
all of the elements to be efficient and automatic.
The number of combinations of the characteristic elements of domestic
oil burners is rather large and accounts for the variety of burners found in
actual practice. Domestic oil burners may be classified as follows:
1. AIR SUPPLY FOR COMBUSTION
a. Atmospheric — by natural chimney draft.
b. Mechanical — electric-motor-driven fan or blower.
c. Combination of (a) and (b) — primary air supply by fan or blower and secondary
air supply by natural chimney draft.
2. METHOD OF OIL PREPARATION
a. Vaporizing — oil distills on hot surface or in hot cracking chamber.
b. Atomizing — oil broken up into minute globules.
(1) Centrifugal — by means of rotating cup or disc.
(2) Pressure — by means of forcing oil under pressure through a small
nozzle or orifice.
(3) Air or steam — by high velocity air or steam jet in a special type of
nozzle.
(4) Combination air and pressure — by air entrained with oil under pressure
and forced through a nozzle.
c. Combination of (a) and (b).
3. TYPE OF FLAME
a. Luminous — a relatively bright flame. An orange-colored flame is usually best
if no smoke is present.
6. Non-luminous — Bunsen-type flame (i.e., blue flame).
4. METHODS OF IGNITION
a. Electric.
(1) Spark — by transformer producing high-voltage sparks. Usually
shielded to avoid radio interference. May take place continuously
while the burner is operating or just at the beginning of operation.
(2) Resistance — by means of hot wires or plates.
b. Gas.
(1) Continuous — pilot light of constant size.
(2) Expanding — size of pilot light expanded temporarily at the beginning
of burner operation.
c. Combination — electric sparks light the gas and the gas flame ignites the oil.
d. Manual — by manually-operated gas torch for continuously operating burners.
5. MANNER OF OPERATION
a. On and off— burner operates only a portion of the time (intermittent).
b. High and low — burner operates continuously but varies from a high to a low
flame.
c* Graduated — busner operates continuously but flame is graduated according to
needs by regulating both air and oil supply.
214
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
A trade classification of oil burners consists of the following general
types : (a) gun or pressure atomizing, (&) rotary and (c) pot or vaporizing.
The gun type, illustrated in Fig. 10 is characterized by an air tube,
usually horizontal, with oil supply pipe centrally located in the tube and
arranged so that a spray of atomized oil is introduced and mixed in the
combustion chamber with the air stream emerging from the air tube. A
variety of patented shapes are employed at the end of the air tube to
influence the direction and speed of the air and thus the effectiveness of
the mixing process.
-fU*£ BOX WIL
FIG. 10. GUN TYPE PRESSURE ATOMIZING OIL BURNER
FIG. 11. CENTER FLAME VERTICAL
ROTARY BURNER
FIG. 12. WALL FLAME VERTICAL
ROTARY BURNER
The most distinguishing feature of vertical rotary burners is the
principle of flame application. These burners are of two general types;
the center flame and wall flame. In the former type, (Fig. 11) the oil is
atomized by being thrown from the rim of a revolving disc or cup and the
flame burns in suspension with a characteristic yellow color. Combustion
is supported by means of a bowl-shaped chamber or hearth. The wall
flame burner (Fig. 12) differs in that combustion takes place in a ring of
215
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
refractory material, which is placed around the hearth. These types of
burners are further characterized by their installation within the ashpit of
the boiler or furnace:
The pot type burner (Fig. 13) can be identified by the presence of a
metal structure, called a pot or retort, in which combustion takes place.
When gun type (pressure atomizing) or horizontal rotary burners are
used the combustion chamber is usually constructed of firebrick or other
suitable refractory material, and is part of the installation procedure.
The oil burners are operated by a small electric motor which pumps the
oil and some or all of the air required. The smallest sizes can generally
burn not much less than 1 gal of oil per hour. The grade of oil burned
ranges from No. 1 to No. 4. No. 4 oil is the heaviest and most viscous of
the various grades mentioned. An oil burner satisfactory for No. 4 oil
can burn any of the lighter grades easily but an oil burner recommended
for No.. 2 oil should never be supplied with the heavier grades. It has been
found that while the heavier grades of oil have a smaller heat value per
FIG. 13. POT TYPE VAPORIZING BURNER
pound, they have, due to greater density, a larger heat value per gallon.
The relative economy of the various grades must be based upon price and
the amount of excess air required for clean and efficient combustion.
Boiler-Burner Units
Boilers and air conditioners especially designed for oil burners are
available to the purchaser of this type of equipment. They are used for
replacements as well as for new installations. This type of equipment
usually has more heating surface than the older coal-burning designs.
Flue proportions and gas travel have been changed with beneficial results.
All problems of combustion chamber design, capacities, efficiencies, etc.,
have been solved. The selection of the proper size of unit should be a
simple process.
COMMERCIAL OIL BURNERS
Liquid fuels are used for heating apartment buildings, hotels, public
and office buildings, schools, churches, hospitals, department stores, as
well as industrial plants of all kinds. Contrary to domestic heating, con-
venience seldom is a dominating factor, the actual net cost of heat pro-
216
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
duction usually controlling the selection of fuel. Some of the largest officfc
buildings have been using oil for many years. Many department stores
have found that floor space in basements and sub-basements can be used
to better advantage for merchandising wares, and credit the heat pro-
ducing department with this saving.
Wherever possible, the boiler plant should be so arranged that either
oil or solid fuel can be used at will, permitting the management to take
advantage of changes in fuel costs if any occur. Each case should be
considered solely in the light of local conditions and prices.
Burners for commercial heating may be either large models of types
used in domestic heating, or special types developed to meet the condi-
tions imposed by the boilers involved. Generally speaking, such burners
are of the mechanical or pressure atomizing types, the former using
rotating cups producing a horizontal torch-like flame. (Fig. 14). As much
FIG. 14. HORIZONTAL ROTATING-CUP OIL BURNER
as 350 gal of oil per hour can be burned in these units, and frequently they
are arranged in multiple on the boiler face, from two to five burners to
each boiler.
The larger installations are nearly always started with a^hand torch,
and are manually controlled, but the useof automatic control is increasing,
and completely automatic burners are now available to burn the twc
heaviest grades of oil. Nearly all of the smaller installations, in schools,
churches, apartment houses and the like, are fully automatic.
Because of the viscosity of the heavier oils, it is customary to heat them
before transferring by truck tank, It also has been common practice to
preheat the oil between the storage tank and the burner, as an aid to
movement of the oil as well as to atomization. This heating is accomplished
by heat-transfer coils, using water or steam from the heating boiler, and
heating the oil to within 30 deg of its flash point.
Unlike the domestic burner, units for large commercial applications
frequently consist of atomizing nozzles or cups mounted on the boiler
front with the necessary air regulators, the pumps for handling the oil
217
HEATING VENTUJWING AIR CONDITIONING GUIDE 1938
and the blowers for air supply being mounted in sets adjacent to the
boilers. In such cases, one pump set can serve several burner units, and
common prudence dictates the installation of spare or reserve pump sets.
Pre-heaters and other essential auxiliary equipment also should be in-
stalled in duplicate.
Boiler Settings
As the volume of space available for combustion is the determining
factor in oil consumption, it is general practice to remove grates and
extend the combustion chamber downward to include or even exceed the
ashpit volume; in new installations the boiler should be raised to make
added volume available. Approximately 1 cu ft of combustion volume
should be provided for every developed boiler horsepower, and in this
volume from 1.5 to 2 Ib of oil can properly be burned. This cor-
responds to a maximum liberation of about 38,000 Btu per cubic foot per
hour. There are indications that at times much higher fuel rates may be
satisfactory. This in turn suggests that the value of 38,000 Btu per cubic
foot per hour might be adjusted according to good engineering judgment.
For best results, care should be taken to keep the gas velocity below 40 ft
per second. Where checkerwork of brick is used to provide secondary air,
food practice calls for about 1 sq in. of opening for each pound of oil
red per hour. Such checkerwork is best adapted to flat flames, or to
conical flames that can be spread over the floor of the combustion chamber.
The proper bricking of a large or even medium sized boiler for oil firing is
important and frequently it is advisable to consult an authority on this
subject. The essential in combustion chamber design is to provide
against flame impingement upon either metallic or fire brick surfaces.
Manufacturers of oil burners usually have available detailed plans for
adapting their burners to various types of boilers, and such information
should be utilized.
The Combustion Process
Efficient combustion, as previously indicated, must produce a clean
flame and must use relatively small excess of air, i.e., between 25 and 50
per cent. This can be done only by vaporizing the oil quickly, completely,
and mixing it vigorously with air in a combustion chamber hot enough
to support the combustion. A vaporizing burner prepares the oil, for
combustion, by transforming the liquid fuel to the gaseous state through
the application of heat. This is accomplished before the oil vapor mixes
with air to any extent and if the air and oil vapor temperatures are high
and the fire pot hot, a clear blue flame is produced. There may be a
deficiency of air as shown by the presence of carbon monoxide (CO) or
an excessive supply of air, depending upon burner adjustment, without
altering the clean, blue appearance of the flame.
An atomizing burner i.e., gun and rotary types is so named because the
oil is mechanically separated into very fine particles so that the surface
exposure of the liquid to the radiant heat of the combustion chamber is
vastly increased and vaporization proceeds quickly. The result of such
practice is the ability to burn more and heavier oil within a given com-
bustion space or furnace volume. Since the air enters the fire pot with the
liquid fuel particles, it follows that mixing, vaporization and burning are
218
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
all occurring at once in the same space. This produces a luminous
instead of a blue or non-luminous flame. In this case a deficient amount
of air is indicated by a dull red or dark orange flame with smoky flame tips.
An excessive supply of air may produce a brilliant white flame in some
cases or, in others, a short ragged flame with incandescent sparks flashing
through the combustion space. While extreme cases may be easily
detected, it is generally not possible to distinguish, by the eye alone, the
finer adjustment which competent installation requires.
Certain tests indicate that there is no difference in economy between a
blue flame and a luminous flame if the position, shape and the per cent of
excess air of both flames are about the same.
Furnace or Combustion Chamber Design
The furnace or combustion chamber may be defined as that part of a
boiler or conditioner in which combustion is established. With burners
requiring a refractory combustion chamber the size and shape should be in
accordance with the manufacturer's instructions. It is important that
the chamber shall be as nearly air tight as is possible, except when the
particular burner requires a secondary supply of air for combustion.
It is evident that the atomizing burner is dependent upon the surround-
ing heated refractory or fire brick surfaces to vaporize the oil and support
combustion. While the importance of the combustion chamber is obvious,
its design has been troublesome. Unsatisfactory combustion may be due
to inadequate atomization and mixing. A combustion chamber can only
compensate for these things to a limited extent. If liquid fuel continually
reaches some part of the fire brick surface, a carbon deposit will result.
Fundamentally, the combustion chamber should enclose a space having a
shape similar to the flame but large enough to avoid flame contact.
The nearest approach in practice is to have the bottom of the combustion
chamber flat but far enough below the nozzle to avoid flame contact,
the sides tapering from the air tube at the same angle as the nozzle spray
and the back wall rounded. A plan view of the combustion chamber thus
resembles in shape the outline of the flame. In this way as much fire brick
as possible is close to the flame so it may be kept quite hot. This insures
quick vaporization, rapid combustion and better mixing by eliminating
dead or inactive spaces in the combustion chamber. An overhanging
arch at the back of the fire pot is sometimes used to increase the flame
travel and give more time for mixing and burning and sometimes to pre-
vent the gases from going too directly into the boiler flues. When good
atomization and vigorous mixing are achieved by the burner, combustion
chamber design becomes a less critical matter. Where secondary air is
used, combustion chamber design is quite important. With some of the
vertical rotary burners considerable care must be exercised in definitely
following the manufacturers instructions when installing the hearth as
in this class successful performance depends upon this factor.
Combustion Adjustments
Where adjustments of oil and air have been made which give efficient
combustion, the problem of maintaining the adjustments constant be-
comes an important one. Particularly is this true when the change
causes" the per cent of excess air to decrease below allowable limits of the
219
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
burner. A decrease in air supply while the oil delivery remains constant
or an increase in oil delivery while the air supply remains constant will
make the mixture of oil and air too rich for clean combustion. The more
efficient the adjustment (i.e., 25 per cent excess air) the more critical it
will be of variations. The oil and air supply rates must remain constant.
The following factors may influence the oil delivery rate: (a) changes
in oil viscosity due to temperature change or variations in grade of oil
delivered, (6) erosion of atomizing nozzle, (c) fluctuations in by-pass relief
pressures and (d) possible variations in methods 2b (3) and 2b (4) listed in
the previous classification table. Note that any change due to partial
stoppage of oil delivery will increase the proportion of excess air. This
will result in less heat, reduced economy and possibly a complete inter-
ruption of service but usually no soot will form.
The following factors may influence the air supply: (a) changes in
combustion draft due to a variety of causes (i.e., changes in chimney
draft because of weather changes, seasonal changes, back drafts, failure
or inadequacy of automatic draft regulator, use of chimney for other
purposes, possible stoppage of the chimney and changes in draft resis-
tance of boiler due to partial stoppage of the flues), and (6) changes in air
inlet adjustments to the fan.
It is recognized that a secondary source of air due to leakage in the
boiler setting is present in many installations and it is highly desirable that
this leakage be reduced to a minimum. Obviously the amount of air
leakage will be determined by the draft in the combustion chamber.
It is important that this draft should be reduced as low as is consistent
with the proper disposal of the gases of combustion. When using mechani-
cal draft burners with average conditions, the combustion chamber draft
should not be allowed to exceed 0.02-0.05 in. water. An automatic draft
regulator is very helpful in maintaining such values,
Measurement of the Efficiency of Combustion.
Efficient combustion being based upon a clean flame and certain
proportions of oil and air employed, it is possible to determine the results
by analyzing the gases formed by the combustion process. An Orsat
apparatus is a device which measures the volume of carbon dioxide
(C02), oxygen (0%) and carbon monoxide (CO) in the flue gases. Except
in the case of a non-luminous flame it is usually sufficient to analyze only
for carbon dioxide (CO*). A showing of 10 to 12 per cent indicates the
best adjustment if the flame is clean. Most of the good installations at
the present time show from 8 to 10 per cent COg. Taking into account
the potential hazard of oil or air fluctuations with low excess air (high
CO*) a setting to give 10 per cent COz constitutes a reasonable standard
for most oil burners. This is particularly true of non-luminous flame
burners which will not function properly with less than 10 per cent COa.
Controls
Oil burner controls may be divided into two parts: (a) devices to
regulate burner operation so the desired house heating result may be
obtained and (&) devices for the safety and protection of the boiler and
burner. For control devices generally consult Chapter 37. The room
thermostat has recently been improved to provide more frequent burner
220
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
operation and greater uniformity' of room temperature. Class (b) controls
comprises a device to shut off the burner if the oil fails to ignite or if the
flame should cease due to lack of oil; a device actuated by steam boiler
pressure to shut off the burner when the pressure reaches some pre-
determined value; a device on the boiler to shut off the burner if the water
level acts too low for safety or one which automatically feeds additional
water to the boiler; a device on warm air furnaces to shut off the burner if
the air temperature gets too high; a valve in the oil supply line which
automatically closes in the event of fire in or near the cellar; and a device
to keep the temperature of the boiler water within certain limits when it is
being used to heat domestic hot water. These devices are all tested and
approved by the Underwriters' Laboratory of Chicago, 111., before they
are offered to the purchaser. The selection of class (&) devices is made by
the oil burner manufacturer.
Fuel Oil Gages
To insure a constant supply of fuel oil and to check deliveries and
consumption it is essential to have accurate means of readily determining
the quantity of oil in the storage tank. For this purpose various types of
indicating or recording gages are used, the simplest forms being the glass
level gage, and a float-and-dial arrangement having a graduated dial face
indicating the proportion of the tank containing liquid. Other more
accurate and dependable devices are designed to operate by hydraulic
action or by hydrostatic impulse. These instruments may be attached to
the tank, giving a direct reading of the liquid contents; or the instrument
itself may be located at a convenient point remote from the tank and
connected with the tank by pipe or tubing. The quantity readings may
be in gallons of liquid, height of liquid level in feet and inches, or in other
desired units of measurement.
GAS-FIRED APPLIANCES
The increased use of gas for house heating purposes has resulted in the
production of such a large number of different types of gas heating
systems and appliances that today there is probably a greater variety of
them than there is for any other kind of fuel.
Gas-fired heating systems may be classified as follows :
I. Gas-Designed Heating Systems.
A. Central Heating Plants.
1. Steam, hot water, and vapor boilers.
2. Warm air furnaces.
B. Unit Heating Systems.
1. Warm air floor furnaces.
2. Industrial unit heaters.
3. Space heaters.
4. Garage heaters.
II. Conversion Heating Systems.
A, Central Heating Plants.
1. Steam, hot water and vapor boilers.
2. Warm air basement furnaces.
221
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
These systems are supplied with either automatic or manual control.
Central heating plants, for example, whether gas designed or conversion
systems, may be equipped with room temperature control, push-button
control, or manual control.
Gas-Fired Boilers
Information on gas-fired boilers will be found in Chapter 13. Either
snap action or throttling control is available for gas boiler operation.
This is especially advantageous in straight steam systems because steam
pressures can be maintained at desired points, while at the same time
complete cut-off of gas is possible when the thermostat calls for it.
Gas-Fired Warm Air Furnaces
Warm air furnaces are variously constructed of cast iron, sheet metal
and combinations of the two materials. If sheet metal is used, it must
be of such a character that it will have the maximum resistance to the
corrosive effect of the products of combustion. With some varieties of
manufactured gases, this effect is quite pronounced. Warm air furnaces
are obtainable in sizes from those sufficient to heat the largest residence
down to sizes applicable to a single room. The practice of installing a
number of separate furnaces to heat individual rooms is peculiar to mild
climates. Small furnaces, frequently controlled by electrical valves
actuated by push-buttons in the room above, are often installed to heat
rooms where heat may be desired for an hour or so each day. These
furnaces are used also for heating groups of rooms in larger residences.
In a system of this type each furnace should supply a group of rooms in
which the heating requirements for each room in the group are similar as
far as the period of heating and temperature to be maintained are con-
cerned.
The same fundamental principle of design that is followed in the con-
struction of boilers, that is, breaking the hot £as into fine streams so that
all particles are brought as close as possible to the heating surface, is
equally applicable to the design of warm air furnaces.
Codes for proportioning warm air heating plants, such as that formu-
lated by the National Warm Air Heating and Air Conditioning Association
are equally applicable to gas furnaces and coal furnaces. Recirculation
should always be practiced with gas-fired warm air furnaces. It not only
aids in heating, but is essential to economy. Where fans are used in con-
nection with warm air furnaces for residence heating, it is well to have the
control of the fan and of the gas so coordinated that there will be sufficient
delay between the turning on of the gas and the starting of the fan to
prevent blasts of cold air being blown into the heated rooms. An additional
thermostat in the air duct easily may be arranged to accomplish this.
Floor Furnaces
Warm air floor furnaces are well adapted for heating first floors, or
where heat is required in only one or two rooms. A number may be used
to provide heat for the entire building where all rooms are on the ground
floor, thus giving the heating system flexibility as any number of rooms
may be heated without heating the others. With the usual type the
register is installed in the floor, the heating element and gas piping being
222
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
suspended below. Air is taken downward between the two sheets of the
double casing and discharged upward over the heating surfaces and into
the room. The appliance is controlled from the room to be heated by
means of a control lever located near the edge of the register. The handle
of the control is removable as a precaution against accidental turning
on or off of the gas to the furnace.
Space Heaters
Space heaters are generally used for auxiliary heating, but may be, and
are in many cases, installed for furnishing heat to entire buildings. With
the exception of wall heaters, they are portable, and can be easily removed
and stored during the summer season. Although they should be connected
with solid piping it is sometimes desirable to connect them with flexible
gas tubing in which case a gas shut-off on the heater is not permitted, and
only A.G.A. approved tubing should be used.
Parlor furnaces or circulators are usually constructed to resemble a
cabinet radio. They heat the room entirely by convection, i.e., the cold
air of the room is drawn in near the base and passes up inside the jacket
around a drum or heating section, and out of the heater at or near the top.
These heaters cause a continuous circulation of the air in the room during
the time they are in operation. The burner or burners are located in the
base at the bottom of an enclosed combustion chamber. The products of
combustion pass up around baffles within the heating element or drum,
and out the flue at the back near the top. They are well adapted not only
for residence room heating but also for stores and offices.
Radiant heaters^ make admirable auxiliary heating appliances to be used
during the occasional cool days at the beginning and end of the heating
season when heat is desired in some particular room for an hour or two.
The radiant heater gives off a considerable portion of its heat in the form
of radiant energy emitted by an incandescent refractory that is heated by
a Bunsen flame. They are made in numerous shapes and designs and in
sizes ranging from two to fourteen or more radiants. Some have sheet-
iron bodies finished in enamel or brass while others have cast-iron or brass
frames with heavy fire-clay bodies. An atmospheric burner is supported
near the center of the base, usually by set screws at each end. Others
have a group of small atmospheric burners supported on a manifold
attached to the base. Most radiant heaters are supported on legs and are
portable; however, there are also types which are encased in a jacket
which fits into the wall with a grilled front, similar to the ordinary wall
register. Others are encased in frames which fit into fireplaces.
Gas-fired steam and hot water radiators are popular types of room heating
appliances. They provide a form of heating apparatus for intermittently
heated spaces such as stores, small churches and some types of offices and
apartments. They are made in a large variety of shapes and sizes and are
similar in appearance to the ordinary steam or hot water radiator con-
nected to a basement boiler. A separate combustion chamber is provided
in the base of each radiator and is usually fitted with a one-piece burner.
They may be secured in either the vented or unvented types, and with
steam pressure, thermostatic or room temperature controls.
Warm air radiators are similar in appearance to the steam or hot water
radiators. They are usually constructed of pressed steel or sheet metal
223
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
hollow sections. The hot products of combustion circulate through the
sections and are discharged out a flue or into the room, depending upon
whether the radiator is of the vented or unvented type.
Garage heaters are usually similar in construction to the cabinet
circulator space heaters, except that safety screens are provided over all
openings into the combustion chamber to prevent any possibility of
explosion from gasoline fumes or other gases which might be ignited by
an open flame. They are usually provided with automatic room tem-
perature controls and are well suited for heating either residence or
commercial garages,
Conversion Burners
Residence heating with gas through the use of conversion burners in-
stalled in coal-designed boilers and furnaces represents a common type
of gas-fired house heating system. In many conversion burners radiants
or refractories are employed to convert some of the energy in the gas to
radiant heat. Others are of the blast type, operating without refractories.
Many conversion units are equipped with sheet metal secondary air
ducts which are inserted through the ashpit door. The duct is equipped
with automatic air controls which open when the burners are operating
and close when the gas supply is turned off. This prevents a large part
of the circulation of cold air through the combustion space of the ap-
pliance when not in operation. By means of this duct the air necessary
for proper combustion is supplied directly to the burner, thereby making
it possible to reduce the amount of excess air passing through the com-
bustion chamber.
Conversion units are made in many sizes both round and rectangular
to fit different types and makes of boilers and furnaces. They may be
secured with manual, push-button, or room temperature control.
The Combustion Process
* Because of the varying composition of gases used for domestic heating
it is difficult to generalize on the subject of gas burner combustion.
Refer to the section on Gas Classification, in Chapter 9.
Combustion Adjustments
Little difficulty should be experienced in maintaining efficient com-
bustion conditions when burning gas. The fuel supply is normally held
to close limits of variation in pressure and calorific value and, therefore,
the rate of heat supply is nominally constant. Since the force necessary to
introduce the fuel into the combustion chamber is an inherent factor of
the fuel, no draft by the chimney is required for this purpose. The use of a
draft diverter insures the maintenance of constant low draft condition in
the combustion chamber with a resultant stability of air supply. A draft
diverter is also helpful in controlling the amount of excess air and pre-
venting back drafts which might extinguish the flame.
Measurement of the Efficiency of Combustion
It is possible to determine the results of combustion by analyzing the
gases of combustion with an Orsat apparatus. It is desirable to determine
224
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
the percentage of carbon dioxide (C02), oxygen (02) and carbon monoxide
(CO) in the flue gases. While ultimate COz values of 10 to 12 per cent may
be obtained from the combustion of gases commonly used for domestic
heating, a combustion adjustment which will show from 8 to 10 per cent
C0a represents a practical value. Under normal conditions no CO will be
produced by a gas-fired boiler or furnace. Limitations as to output rating
by the A.G.A. are based upon operation with not more than 0.04 per cent
CO in the products of combustion. This is too small an amount to be
determined by the ordinary flue gas. analyzer.
Controls
Gas burner controls may be divided into two parts: (a) devices to
regulate burner operation so that the desired house heating results may be
obtained and (b) devices for the safety of the boiler and burner. Control
devices are treated in detail in Chapter 37. A room thermostat may be
used as a control of house heating effect. These may be obtained in a
number of types. Some central heating plants are equipped with push-
button or manual control. Class (&) controls include a device to shut off
the burner if the gas fails to ignite, a device actuated by boiler pressure,
water temperature, or furnace bonnet temperature to shut off the burner
when the pressure or temperature becomes excessive, a device on the
boiler to shut off the burner if the water level falls below safe limits or one
which automatically feeds additional water to the boiler, and a device for
controlling the gas pressure within desired limits. The main gas valve
may be either of the snap action or throttling type.
Sizing Gas-Fired Heating Plants
While gas-burning equipment can be and usually is so installed as to be
completely automatic, maintaining the temperature of rooms at a pre-
determined and set figure, there are in use installations which are manually
controlled. Experience has shown that, in order to effectively overcome
the starting load and losses in piping, a manually-controlled gas boiler
should have an output as much as 100 per cent greater than the equiva-
lent standard cast-iron column radiation which it is expected to serve.
Boilers under thermostatic control, however, are not subject to suclr
severe pick-up or starting loads. Consequently, it is possible to use $
much lower selection, or safety factor. A gas-fired boiler under thermo
static control is sensitive to variations in room temperatures so that ii
most cases a factor of 20 per cent is sufficient for pick-up load.
The factor to be allowed for loss of heat from piping, however, mus
vary somewhat, the proportionate amount of piping installed being con
siderably greater for small installations than for large ones. Consequent!
a selection factor for thermostatically controlled boilers must be variable
Liberal selection factors to be added to the installed steam radiatio
under thermostatic control are given in Fig. 3 of Chapter 13.
Appliances used for heating with gas should bear the approval seal <
the American Gas Association Testing Laboratory. Installations shoul
be made in accordance with the recommendations shown in the publ
cations of that association.
225
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Ratings for Gas Appliances
Since a gas appliance has a heat-generating capacity that can be pre-
dicted accurately to within 1 or 2 per cent, and since this capacity is not
affected by such things as condition of fuel bed and soot accumulation,
makers of these appliances have an opportunity to rate their product in
exact terms. Consequently all makers give their product an hourly Btu
output rating. This is the amount of heat that is available at the outlet of
a boiler in the form of steam or hot water, or at the bonnet of the furnace
in the form of warm air. The output rating is in turn based upon the
Btu input rating which has been approved by the American Gas Asso-
ciation Testing Laboratory and upon an average efficiency which has
been assigned by that association.
In the case of boilers, the rating can be put in terms of square feet of
equivalent direct radiation by dividing it by 240 foi steam, and 150 for
water. This gives what is called the A merican Gas Association rating, and
is the manner in which all appliances approved by the American Gas
Association Laboratory are rated. To use these ratings it is only necessary
to increase the calculated heat loss or the equivalent direct radiation load
by an appropriate amount for starting and piping, and to select the boiler
or furnace with the proper rating.
The rating given by the American Gas Association Laboratory is not
only a conservative rating when considered from the standpoint of
capacity and efficiency, but is also a safe rating when considered from the
standpoint of physical safety to the owner or caretaker. The rating that
is placed upon an appliance is limited by the amount of gas that can be
burned without the production of harmful amounts of carbon monoxide.
This same limitation applies to all classes of gas-consuming heating
appliances that are tested and approved by the Laboratory. Gas boilers
are available with ratings up to 14,000 sq ft of steam, while furnaces with
ratings up to about 500,000 Btu per hour are available. (See Chapter 20.)
REFERENCES
Stoker Information, Bulletin No. 5, Committee of Ten, 307 N. Michigan Ave.,
Chicago, III.
Domestic Burners for Pennsylvania Anthracite, Commercial Standard CS48-34
U. S. Department of Commerce.
Performance Expectancy of Domestic Underfeed Stokers for Anthracite, by Allen J.
Johnson (Transactions, A.I.M.E., Coal Division, Vol. 119, 1936).
The Relation of the Size of Bituminous Coals to Their Performance on Small Under-
feed Stokers — The Relation of the Size in the Hopper to That Burned in the Retort,
by R. A. Sherman and E. R. Kaiser, Technical Report No. 1, Bituminous Coal Research,
Inc., (December, 1935) Pt. I.
The Relation of the Size of Bituminous Coals to Their Performance on Small Under-
feed Stokers — Burning Tests on Four Typical Coals, by R. A. Sherman, E. R. Kaiser and
H. R. Limbacher, Technical Report No. 1, Bituminous Coal Research, Inc. (July, 1937)
Pt. II.
Stoker Coals, Anonymous, Bulletin of Chesapeake and Ohio Railway Co., 1935.
Study of Performance Characteristics of Oil Burners and Low Pressure Heating
Boilers, by L. E. Seeley and E. J. Tavanlar (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931,
p. 517).
A Study of Intermittent Operation of Oil Burners, by L. E. Seeley and J. H. Powers
(A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 317).
226
CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT
Air Supply and Its Effect on Performance of Oil Burners and Heating Boilers, by
L. E. Seeley," J. H. Powers and E. J. Tavanlar (A.S.H.V.E. TRANSACTIONS, Vol. 39, 1933,
p. 7,5).
Study of Fuel Burning Rates and Power Requirements of Oil Burners in Relation to
Excess Air, by L. E. Seeley and E. J. Tavanlar (A.S.H.V.E. TRANSACTIONS, Vol. 40,
1934, p. 319).
Oil Burning in Residences, by D. W. Nelson (A.S.H.V.E. TRANSACTIONS, Vol. 41,
1935, p. 355).
Domestic Oil Burners, by A. H. Senner (Mechanical Engineering, November, 1936).
A Study of Oil-Fired Heating Boilers, by R. C. Cross and \V. R. Lyman (Heating and
Ventilating, October, 1931).
Value of Oil Burner Installation Surveys, by R. C. Cross and W. R. Lyman (Heating
and Ventilating, January, 1931).
House Heating, Industrial Gas Series, American Gas Association.
Approval Requirements of Central House Heating Gas Appliances, American Gas
Association.
A Method for Determining Fuel Burning Rates in Heating Boilers Fired by Auto-
matic Devices, by R. C. Cross (Heating and Ventilating, January, 1932).
Heat Losses and Efficiencies of Fuels in Residential Heating, by R. A. Sherman and
R. C. Cross (A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air Conditioning,
January, 1937, p. 53).
Efficiencies and Costs of Various Fuels in Domestic Heating, by R. A. Sherman and
R. C. Cross, Technical Report No. 3, Bituminous Coal Research, Inc., (December, 1936).
Automatic Heating Equipment, American Architect Reference Data, No. 7, September,
1933.
PROBLEMS IN PRACTICE
1 • List some factors which might account for higher efficiencies with stoker
firing than with hand firing.
a. The uniform rate of coal feed, b. Better distribution in the fuel bed, and c. Positive
control of the air supplied for combustion.
2 • Classify stokers as to construction and operation.
a. Overfeed flat grate, b. Overfeed inclined grate, c. Underfeed side cleaning type, and
d. Underfeed rear cleaning type.
3 • What classification may he made of stokers as to their use?
Class 1. For residences (Capacity up to 60 Ib of coal per hour).
Class 2. For apartment houses and small commercial heating plants (Capacity 60 to IOC
Ib of coal per hour).
Class 3. For medium sized commercial heating plants (Capacity 100 to 300 Ib of coa
per hour).
Class 4. For large commercial plants and small high pressure steam plants (Capacity
300 to 1200 Ib of coal per hour).
4 • What main parts are found in an underfeed residential stoker?
A hopper is supplied to hold coal which is fed by a screw or plunger into a retort provide
with air openings called tuyeres. A blower supplies air under pressure for combustion, an
a gear case provides for changes in coal feeding rates.
5 • What is a dead-plate?
A dead-plate is a flat surface without air supply openings upon which the fuel rests whi
combustion of the fixed carbon is completed. Generally the ash is removed from tl
dead-plate.
227
HEATING VENTUJLTING AIR CONDITIONING GUIDE 1938
6 • What features of furnace design are essential for the proper burning of
the volatile coal gases above the fuel bed?
Adequate provisions should be made so that the furnace volume is sufficiently liberal
and that the grates are a sufficient distance from the heating surfaces to permit the
proper combustion of gases-
7 • What methods of oil atomization are used?
a. Throwing the oil from a rotating cup or disc, b. Forcing the oil under high pressure
through a nozzle, c. Propelling the oil with a high velocity jet of air or steam, and d.
Forcing an oil and air mixture through a nozzle.
8 • What is the purpose of atomization?
Atomization is used to increase the surface area of the oil in order to facilitate putting it
into a vaporous state so it may burn.
9 • Is the furnace of much importance in oil burning?
In most cases it is very important. It is the function of the oil burner to supply the air
and fuel in correct proportions; the furnace must provide heated space for proper mixing
and combustion.
10 • Which flame is considered better, the luminous or the non-luminous?
Laboratory tests show that they are equally efficient in the usual installation.
11 • How should oil burner adjustments be made?
Adjustments should be made by an experienced man who uses a gas analysis apparatus
to determine the COz content.
12 • What CO2 content should be attained in oil burning?
Ten per cent COt is considered good practice, for it indicates the supplying of 50 per cent
excess air.
13 • What maximum heat release is considered good practice in oil burning?
A heat release of 38,000 Btu per cubic foot per hour is considered to be the maximum for
average large installations. This figure has been greatly exceeded in some cases. _The
design of the combustion chamber, as to impingement of flame and as to proper mixing
at high temperatures, has much to do with the attainable heat release.
14 • Name five types of gas-fired space heaters.
a. Parlor furnaces or circulators.
b. Radiant heaters.
c. Gas-fired steam or hot water radiators.
d. Warm air radiators.
«. Garage heaters.
15 • How are gas heating units rated?
Gas-fired units are rated on the basis of output in Btu per hour.
16 • What safety consideration is noted in establishing the ratings of gas-fired
units?
The rating is limited by the amount of gas that can be burned without the liberation of
harmful amounts of carbon monoxide.
228
Chapter 12
HEAT AND FUEL UTILIZATION
Total Heat Loss Requirements, Utilization Factors, Degree-
Day Methods, Base Temperature Determinations, Steam
Consumption of Buildings, Fuel Consumption, Maximum
Demands, Load Factors
/HTVHE hourly heat loss (If) is equal to the sum of the transmission
1 losses (fit) and the infiltration losses (Hi) of the rooms or spaces to
be heated. The total equivalent heating surface required is equal to
In estimating the fuel consumption of a building of more than one
room divided by walls or partitions, it is not correct to use the calculated
heat loss of the building without making the proper allowances for the
fact that the heating load at any time does not involve the sum of the
infiltration losses of all the heated spaces of the building but only part of
the infiltration losses. This is explained in Chapter 6.
It is sufficiently accurate in most cases to consider only half of the total
infiltration losses of a building having interior walls and partitions. The
value of H in Equation 1 would, under these conditions, be equal to
Hi + -~. In some cases, where the building has no interior walls or
2>
partitions, the infiltration losses are calculated by using only half of the
total crack. In this case the entire infiltration loss should be considered.
The heat required to warm the cold building and contents is a factor to
be considered. Under certain conditions the cooling of the structure and
contents will, to some extent, compensate for the heat required to rewarm
the building. For example, if the building is under thermostatic control
and the day and night temperatures are, 70 F and 50 F respectively, there
will be a period during which no heat will be added while the building is
cooling to 50 F, and the saving resulting therefrom will correspond to the
additional heat required to bring the building and contents back to the
daytime temperature.
ESTIMATING FUEL CONSUMPTION
There are two methods in use for estimating heat or fuel consumption.
One method is theoretical, based on a calculated heat loss and assuming
absolute constant temperatures for very definite hours each day through-
out the entire heating season. It does not take into account factors which
are difficult to evaluate such as opening of windows, abnormal heating of
the building, sun effect, poor heating systems, etc.
229
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
The second method is based on steam consumption data which have
been taken from a group of buildings in operation, and the results com-
puted on a degree-day basis. While this method may not be as theo-
retically correct as the first mentioned method, it is of more value for
practical use. Calculations of heat consumption made by the second
method will invariably be higher than calculations made by the first
method.
Theoretical Estimation Method
To predict the amount of fuel likely to be consumed in heating a
building during a normal heating season, it is necessary to know the total
heat requirements of the building and the utilization factor of the fuel.
The accuracy of the estimate will depend on the ability to select these
values and on the care taken in making allowances for other variable
factors.
Heat requirements are given by the following general formula:
Steam requirements are determined by dividing the above by 1000,
thus:
fa - to) 1000
Fuel requirements may be determined by the following formula:
(2)
where
t =s inside temperature, degrees Fahrenheit.
id = inside design temperature, degrees Fahrenheit.
/a = average outside temperature, degrees Fahrenheit (Table 2, Chapter 7).
2o — outside design temperature, degrees Fahrenheit.
H = calculated heat loss of building based on outside temperature (/o), Btu per hour.
N = number of heating hours per season; 5088 from October 1 to May I1.
M = heat loss, Btu per season.
5 = steam required to supply M Btu of heat loss.
F = quantity of fuel required per heating season.
C — calorific value of one unit of fuel, the unit being the same as that on which
F is based.
E = efficiency of utilization of the fuel, per cent.
Example 1. A small factory building located in Philadelphia is to be heated to 60 F
between the hours of 7 A.M. and 7 P.M., and to 50 F during the remaining hours. The
calculated hourly heat loss based on a design temperature of — 6 F is 500,000 Btu. If
coal having a calorific value of 12,500 Btu is fired and the overall heating efficiency is
assumed to be 60 per_cent, how many pounds of steam would be required for a normal
heating season?
lThis is the period for which t* (Table 2, Chapter 7) is calculated. If the heating season is different
than this period, the corrected values may be substituted for N and t*.
230
CHAPTER 12. HEAT AND FUEL UTILIZATION
Solution. Since there are no partitions in the building, the entire heat loss is con-
sidered. From Table 2, Chapter 7, the average outside temperature ('fe) during the
heating season is 42.7 F; N for the period for which fe. is taken (October 1 to May 1) is
5088; H = 500,000; to « -6 F; * = 50 F and 60 F; fo = 60 F; E = 00 per cent
average for heating season; C - 12,500.
The average daily temperature for the 24 hours is:
50 X 12 + 60 _X 12 ^ 55
Substituting in Equation 1:
M = 500,000 X (55 - 42.7) X 5088
60 -(-6)
S = 474,100 Ib of steam.
nor,
.x- * 63,200 Ib of coal = 31.5 tons.
Practical or Degree-Day Method
The amount of heat required by a building depends upon the outdoor
temperature, if other variables are eliminated. Theoretically it is pro-
portional to the difference between the outdoor and indoor temperatures.
Some^years ago the American Gas Association* determined from experi-
ment in the heating of residences that the gas consumption varied directly
as the difference between 65 F and the outside temperature. In other
words, on a day when the temperature was 20 deg below 65 F, twice as
much gas was consumed as on a day when the temperature was 10 deg
below 65 F. The degree day is defined in Chapter 45. Degree-days for
various cities in the United States and Canada are given in Table 1.
Establishing the Base Inside Temperature. Recently the National
District Heating Association has studied the metered steam consumption
of 163 buildings3 in 22 different cities and has published data substanti-
ating the fact that the 65 F base originally chosen by the gas industry is
approximately correct.
The steam consumption of each building by months was divided by the
number of days in each month, thus giving the average daily steam con-
sumption by months. The average steam consumption was then plotted
against the average monthly temperature, as shown in Fig, 1, and the
temperature at which a line drawn through the points crossed the base
line indicated the temperature corresponding to zero steam consumption,
or the base temperature. The composite results from 163 buildings
calculated in this manner are shown in Table 2.
The resultant average of 66.0 F is close to the A.G.A. figure of 65 F.
It will be noted that the base temperature calculated for hotels, apart-
ments and residences is consistently higher than those for such buildings
as garages, auto sales buildings, and manufacturing buildings. This, of
course, would be expected in view of the higher inside temperatures
carried in the former group; in fact, an even greater difference would be
3See Industrial Gas Series, House Heating (third edition) published by the American. Gas Association.
'These buildings are all served with steam from a district heating company.
231
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 1. DEGREE-DAYS FOR CITIES IN THE UNITED STATES AND CANADA*
STATE , Cnr
JAN.
FEB.
MAR.
APR.
MAY
SEPT
OCT.
Nov
DEC
TOTAL
Ala
Ariz
Ark
Calif
Col..
Birmingham
Mobile
. 589
. 428
.1153
459
577
311
969
325
260
152
i 896
257
69
318
186
840
252
595
394
1128
465
"651
301
428
1067
1017
1017
2408
1471
7145
1845
2665
2811
1504
3264
6553
5873
5895
4626
890
2891
1490
4558
4924
6315
5370
4164
5297
6373
7023
5034
5301
4616
4180
1023
8531
7012
4533
6045
6464
6494
8692
9480
7851
1822
5202
4585
7115
8699
6231
6128
5891
6852
5175
4934
6063
6889
6821
5348
6785
3234
2302
8498
"577
Flagstaff
Tucson
Hot Springs
654
87
636b
292d
Little Rock
719
i 326
! 465
1085
1079
1110
582
266
356
993
918
1011
353
239
354
884
799
899
78
159
294
612
534
543
"96"
458b
459b
267
223
502c
162
72
39
47
"146
502
428
360
381
123
261
789
759
693
"™7S
396
201
738
Los Angeles._
San Francisco
Colorado Springs..
Denver.-
Conn....
D. C
New Haven™
Washington
Fla.
Ga.
Jacksonville
Atlanta „ .
285
682
409
1098
207
558
316
848
56
388
167
651
"m
235"
108""
""96
*434
267
639
397
1011
Idaho
Savannah.
Boise
435
III
Lewiston
Chicago
1262
1180
949
1128
1392
1434
1116
1221
974
939
332
1380
1321
955
1150
1095
1008
854
969
1173
1386
890
980
867
801
230
232
168
843
042
909
760
640
756
890
967
688
741
648
589
58
1110
1017
700
908
549
365
276
384
429
489
342
339
342
264
"786
642
348
570
248
56
"58"
118
164
46
30
"33"
353
282
155
298
357
415
276
270
245
186
756
681
528
687
798
870
672
699
612
552
102
843
780
567
693
"777
960
062
963
252
605
597
909
041
1113
1038
862
1017
1216
1265
1004
1051
903
849
301
1228
1153
875
1026
lTl3
1301
1491
1405
471
1038
936
192
383
"174
974
234
893
930
073
147
104
955
140
694
527
Ind
Iowa
Kans —
Ky
La
Springfield.-
Evansville
Indianapolis
Des Moines._
Sioux City._
Dodge City
Topeka
Lexington
Louisville.-
New Orleans
25
Me._
Md
Mass..
Eastport
Portland
Baltimore.
Boston
843b
368
22
245
226"
682b
22b
35
566^
120
543
443
223
363
"5)0
567
620
481
"285
205
524
620
328
452
484
254
242
459
446
418
276
426
130
19
48
~42~
268<i
298d
93
Mich
Minn —
Springfield
Detroit.
Marquette.
Duluth
1253
1501
1727
1609
520
?01
134
360
473
400
384
987
854
120
450
125
823
240
903
942
902
142
156
960
181
630
468
976
249
277
095
195
750
657
955
168
868
753
Oil
806
735
775
980
032
837
991
446
322
573
804
810
570
Miss
Mo
Minneapolis
Vicksburg
Kansas City
St. Louis
Billings
Havre.
Lincoln
Omaha
Reno
321
276
534
630
414
534
669
519
402
543
549
675
486
587
183
108
15
76b
13
84*"
56b
Sib
20
81
Olb
93
47
55
44
Mont
Nebr
Nev.
1060
1316
1624
1355
1041
1349
992
014
110
286
240
061
242
722
555
89
70
S"
68
20"
72
75
87"
780
714
846
588
588
780
774
774
618
787
429
303
N. H
Concord
N. J _
Atlantic City
N. M „
N. Y
N. C
NT. Dak
Trenton
Santa Fe
Albany.
Buffalo
New York
Utica
Raleigh
Wilmington
Bismarck.
•Heating and Ventilating Degree-Day Handbook.
o Including June.
clncluding July and August,
d Including August.
232
CHAPTER 12. HEAT AND FUEL UTILIZATION
TABLE 1. DEGREE-DAYS FOR CITIES IN THE UNITED STATES AND CANADA* (Continued)
STATE
Crrr
JAN.
FEB.
MAE.
APR.
MAT
SlPT.
OCT.
Nov.
DEC.
TOTAL
Ohio
Okla
Oree.
Cincinnati
Cleveland
Columbus
Oklahoma City.
Portland
1076
1180
1113
865
806
910
1075
980
742
644
747
950
703
465
558
378
564
420
162
402
73
220
87
335~b
Tf
165"
290
366
313
105
332
675
732
690
459
558
980
1060
1017
815
728
5129
6154
5323
3613
4468
4629
4855
5235
6014
1769
3257
7683
2950
3578
1578
2455
1157
1202
6735
5553
7620
4243
3349
3725
4968
6353
5016
4884
7612
7823
7290
7372
7462
v &
Pa
R. I
g^ £
S. Dak
Tenn
Texas
Utah
Vt...
Va
Wash
W. Va
Wis
Wyo
Salem.
Philadelphia
Pittsburgh.
Providence.
Charleston.
Spartanburg
Sioux Falls
Memphis
Nashville _
Austin
1001
1054
1116
487
725
"744
812
895
944
1069
372
688
"599
747
756
787
890
242
431
"384
476
402
423
558
36
147
""96
180
68
78
251
"63"
242
313
«54o
"iTl"
_
136
588
669
693
207
429
"402
483
903
967
1026
425
716
"663
744
"335
347
1218
1020
1286
878
685
765
716
1057
977
1328
1322
1280
1222
1143
Dallas
Houston—
San Antonio
Logan ...
Salt Lake City....!!
Burlington
Fredericksburg
Norfolk
Io6
381
1260
1110
1535
887
738
825
775
1171
1026
1507
1538
1535
1383
1215
"277
274
1072
885
1294
820
650
702
653
952
944
1321
1358
1265
1328
1075
"~65
74
893
722
1089
583
520
552
623
778
713
1046
1125
1032
1023
995
376"
234
276b
"468
388
481
223
99
158
403
514
294
"493
505
462
449
605
Tl4
126
819
723
861
549
411
483
570
819
648
"921
921
909
846
900
~iiT
18
144
525
453
654
303
246
240
465
504
414
"603
600
528
648
720
Richmond
Seattle
Spokane.
Morgantown
Parkersburg
Fond du Lac.
Green Bay.
LaCrosse
487b
366
276"
322
183
389*>
569
276=
192
117"
132
96
84
240
Milwaukee.
Cheyenne.
PROVINCE
Cm
JAN.
FEB.
MAE.
APR.
MAT
SEPT.
OCT.
Nov.
Die.
TOTAL
B. C.
Victoria
5777
Alb
Vancouver.
Kamloops
Medicine Hat._
5976
6724
8152
Sask
Man
Qu'Appelle.
Winnipeg-
11,261
11,166
Ont
Port Arthur.
Toronto -... .
10,803
7732
Que
N. B
N. S
P. E. I.....
Montreal
Quebec
Fredericton
Yarmouth
Charlottetown
1615
1409
1219
720
309
190
372
961
1422
8417
8628
9099
7694
8485
aHeating and Ventilating Degree-Day Handbook.
^Including June,
elududing July and August.
233
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
TABLE 2. BASE TEMPERATURE FOR THE DEGREE-DAY**
TTPI or BUILDING
No. OF BUILDINGS
ANALYZED
TEMPERATURE F COR-
RESPONDS TO ZERO
STEAM CONSUMPTION
Office
60
4
3
2
6
11
12
7
14
S
4
5
3
2
2
4
3
3
2
8
66.2
65.8
66.2
65.5
67.4
64.0
64.3
66.5
68.8
66.9
65.5
64.9
67.6
65.8
64.8
61.2
67.7
67.7
65.2
65.4
Office and Bank.
Bank
Office and Telephone Exchange
Office and Stores
Stores. ._ .
Department Stores
Hotels........ .„ „..._. „
Apartments. _
Residences.
Clubs
Lodges _
Theatres...
Churches.
Garage.
Auto Sales and Service.
Newspaper and Printing
Warehouse and Loft
Office and Loft.
Manufacturing
Average for 163 Buildings
66. OF
•Report of Commercial Relations Committee, 19S£ Proceedings, National District Heating Association.
TABLE 3. STEAM CONSUMPTION FOR VARIOUS CLASSES OF BuiLDiNGsa
(Heating Season Only)
BUILDING CLASSIFICATION
No. OF
BUILDINGS
STEAM CONSUMPTION
POUNDS PER DEGREE-DAT— 65 F BASIS*
Per M Cu Ft
of Heated
Space
Per M Sq Ft
of Radiatorc
Surface
PerMBto
perHrof
HeatLossb
Apartments
16
10
12
7
10
18
6
16
7
8
6
14
6
35
35
1.78
1.46
1.32
1.25
0.96
0.90
0.90
0.89
0.88
0.83
0.58
0.57
0.42
1.09
0.975
97.5
80.6
64.2
105.5
77.0
80.6
75.0
72.3
45.2
62.2
49.4
60.7
72.3
70.0
65.4
0.359
0.371
Hotels
Residences
Printing
Clubs and Lodges.
Retail Stores
Theatres. ..
0.268
0.498
0.283
Loft and Mfg _
Banks
Auto Sales and Service
Churches
67238
Department Stores.
Garages (Storage)6. _
Offices (Total) „.
0.283
0.256
Offices (Heating only)
•Includes steam for heating domestic water for heating season only.
BHeat loss calculated for maximum design condition (in most cases 70 F inside, zero outside).
cEquivalent steam radiator surface.
dThe figures are a numerical— not a -weighted — average for the several buildings in each class.
"Based on zero consumption at 55 F.
234
CHAPTER 12. HEAT AND FUEL UTILIZATION
expected. For an average figure, the A .G.A . base of 65 F may therefore be
safely used, and if greater refinement is desired, the figure for the type of
building under consideration can be taken from Table 2.
Table 34 gives the steam consumption per degree-day, expressed in
three different ways, for 196 buildings in 14 different classifications.
These buildings are divided among 21 different cities in the United States.
The steam used for heating the domestic water is included in these
figures, but in the case of office buildings, the steam for heating only is
also shown. The data are placed on a comparable basis by expressing
the steam consumption in terms of pounds per degree-day per thousand
square feet of equivalent installed radiator surface, per thousand cubic
feet of heated space, and per thousand Btu of calculated heat loss.
3 PER DAY
<?
V
\
3 —
X
^
^
\
STEAM CONSl
\
\
\
AVERAGE !
\
^
\
AVERAGE TEMPERATURE FOR MONTH DEG F
FIG. 1. METHOD OF DETERMINING BASE TEMPERATURE FOR
DEGREE-DAY CALCULATIONS6
The choice of these units of comparison require some explanation.
The use of heated space in preference to the gross cubage used by architects
is obviously more accurate for this purpose. The architect's cubage
includes the outer walls and certain percentages of attic and basement
space which are usually unheated. The net heated space is usually about
80 per cent of the gross cubage and can be calculated from the latter if it
cannot be measured. The cubical content is somewhat inaccurate as a
basis of comparison due to differences in types of construction, exposure,
and ratio of exposed area to cubical contents.
The use of radiator surface as the basis of comparison has two ob-
jections. One is that the amount of radiator surface in a building is often
either excessive or deficient, and figures for steam consumption based on
it are therefore likely to be in error. Another reason is that it is difficult
to convert fan coil surface into equivalent direct radiator surface with
accuracy. On the whole, the use of radiator surface as the basis of com-
parison is the least satisfactory of the three methods.
*The Heat Requirements of Buildings, by J. H. Walker and G. H. Tuttle (A.S.H.V.E. TRANSACTIONS,
Vol. 41, 1935, p. 171).
•Report of Commercial Relations Committee, 198& Proceedings, National District Seating Association.
235
HEATING VENTILATING Am CONDITIONING GUIDE 1938
It should be noted that the figures in Table 3 are for the heating season
only and include steam for heating domestic water.
Example 1 solved by the degree-day method and using values taken
from Table 3 would show a higher steam consumption.
Example 8. Factor for steam consumption for a manufacturing building per M Btu
per hour heat loss per degree-day - 0.283; total number of degree-days per year (Table 1)
- 4855; heat loss = 500,000 Btu per hour.
Solution. 0.283 X 4855 X 500 - 686,982 Ib of steam per year. This calculation
results in an estimate 45 per cent higher than the previous calculation and one which
would be more nearly correct for actual practice.
TOO
600
500
J400
5300
200
100
120
100
80
O
20
I 234567B9
STEAM CONSUMPTION - MILLION LB
FIG. 2. CURVE FOR ESTIMATING FUEL CONSUMPTION FOR VARIOUS
KNOWN STEAM CONSUMPTION*
•This curve is based on heating efficiencies of 60 to 70 per cent for coal and oil, respectively, a calorific
value of coal of 13,000 Btu per pound, a calorific value of oil of 140,000 Btu per gallon.
In case the heat loss figure is not known this method of estimating heat
or steam consumption can also be applied if the net heated space figure
is available.
CALCULATION OF FUEL CONSUMPTION
After the heat and steam consumption of the building have been calcu-
lated, ^ the corresponding fuel requirements may also be estimated by
assuming the correct boiler and furnace efficiencies. If the building is to
be supplied with steam from a district heating company, the steam con-
sumptions as calculated by the two Methods are generally assumed to be
correct. However, if the steam is to be supplied from an individual boiler
236
CHAPTER 12. HEAT AND FUEL UTILIZATION
unit, the consumption should be assumed as from 10 to 20 per cent greater.
One reason for this difference in steam consumption is that district steam
is a metered^ service, and building managers are therefore more conscious
of their heating costs, which generally results in better maintained heating
systems. Also, the district steam service is usually installed with ther-
mostatic control which reduces overheating to a minimum.
Fig. 2 shows the amount of coal or oil that may be estimated when the
steam consumption is known. Assuming the steam consumption that
1.4
\
1.2
1-Cu ft of gas per sq ft installed
hot water radiation
2-Cu ft of gas per sq ft installed
steam radiation
3- Cu ft of gas per 100 cu ft bldg
contents hot air system
4- Cu ft of gas per 1,000 Btu hourly
loss from bldg. hot air system
200
500 600 700
Btu VALUE OF GAS
800
900 1,000 1,100
FIG. 3. CHART GIVING GAS REQUIREMENTS PER DEGREE-DAY FOR VARIOUS CALORIFIC
VALUES OF GAS AND FOR DIFFERENT HEATING SYSTEMS*
aTbis chart is based on an inside temperature of 70 F and an outside temperature of zero. If the radia-
tion is installed on the basis of any other temperature difference, multiply the result obtained from this
chart by 70, and divide by the actual temperature difference. From Industrial Gas Series House Heating,
(third edition) published by the A merican Gas Association.
was calculated in Example 2, 686,982 Ib, the corresponding coal con-
sumption, from the curve, is 44 tons and the oil consumption 6000 gal.
Fig. 3 indicates the average gas consumption per degree-day for
various heat contents. While the fuel consumption in individual cases
may vary somewhat from the curve values, these average values are
sufficiently accurate for estimating purposes and give satisfactory results.
The value generally used in the manufactured gas industry for resi-
dences is 0.21 cu ft per degree-day per square foot of equivalent steam
radiation (240 Btu) based on the theoretical requirements. A correction
for warmer climates is necessary and it is customary to gradually increase
the relative fuel consumption below 3000 degree-days to about 20 per cent
more at 1000 degree-days.
237
§g
*l
- Si
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
§ CALORIFIC VALUE OF FUEL
J BTU PERLS -AS FIRED
,0-1 K>-
I I
100 ' 20O 300
GROSS OUTPUT -THOUSAND BT.U PER HOUR
46 8 10 12 14
GROSS OUTPUT- HUNDRED FEET STEAM RADIATION
5 10 15 20 25
GROSS OUTPUT - HUNDRED FEET WATER RADIATION
FIG. 4. COAL FUEL BURNING RATE CHART.
I2
SB*
H*
*!'
100 200 300
GROSS OUTPUT-THOUSAND BTU PER HOUR
400
500
—i 1 1 1 1 1 1 1 1 1 1 1
4 6 8 10 12 14
GROSS OUTPUT- HUNDRED FEET STEA'M RADIATION
i i i 1 —
18 20
0 5 10 15 -20 25 30
GROSS OUTPUT- HUNDRED FEET WATER RADIATION
FIG. 5. OIL FUEL BURNING RATE CHARTS
nil !lbj?o2art S-kf8^ upon No: 3 9a Caving a heat content of 143,400 Btu per gallon. If other grades of
2l^2n^iI?S?9l|fe oe ^fe ?%fined from this chart by the following factors: No. 1 oil (139,000 ^Btu
SdfffiSawSi » 4£i?D^n? 25 S ffi^WJSSi 5?,; lilflttKPnSS11 per »**> a"2» No-
238
CHAPTER 12. HEAT AND FUEL UTILIZATION
For hot water or warm air heat the fuel consumption is about 0.19 cu ft
per degree-day per square foot of equivalent steam radiation, that is, per
240 Btu per hour. The actual requirements likewise relatively increase
with hot water or warm air systems as the number of degree-days decreases
below 3000. For larger installations, that is 1000 sq ft of theoretical
radiation and above, there is an increase in efficiency, and a consequent
decrease in the fuel consumption per degree-day per square foot of
heating surface.
The approximate quantities of steam required in New York City per
square foot of heating surface for various classes of buildings are given in
Chapter 42.
The preceding discussion on fuel consumption has dealt with the
heating requirements of the building irrespective of any air that may be
GROSS CALORIFIC VALUE
O O BT.U PER CUBIC FOOT
CO O
800- 500-
300-
200-
200-
100-
300
100
. L
100 200 300
GROSS OUTPUT -THOUSAND &T.UL PER HOUR
500
4 6 8 10 12 14
GROSS OUTPUT- HUNDRED FEET STEAM RADIATION
05 IO 15 20 25 30
GROSS OUTPUT - HUNDRED FEET WATER RADIATION
FIG. 6. GAS FUEL BURNING RATE CHART.
introduced for ventilation purposes other than the normal infiltration of
outside air. The heat required for warming air brought into the building
for ventilation may be estimated from data given in Chapters 3 and 21.
Rate of Fuel Burning
If the estimated maximum load or gross output is determined as out-
lined in Chapter 13, the fuel burning rates for coal, oil, or gas may be
determined from the charts illustrated in Figs. 4, 5 and 6. For a given
efficiency, the rate of fuel burning is directly proportional to the gross
output, and therefore, these charts can be extended by moving the
decimal point the same number of digits in both vertical and horizontal
scale. All charts are based upon values of one square foot steam radiation
equivalent to 240 Btu per hour and one square foot hot water radiation
equivalent to 150 Btu per hour. In using these charts, consideration
239
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
must be given to the overall efficiency of the boiler or firing device. This
factor is largely dependent upon good judgment and is a measure of the
degree of efficiency to be expected from a particular installation.
The correct fuel burning rate can be determined directly from the
several charts for oil or gas burning installations, as these customarily
operate on a strictly intermittent basis. These fuel burning devices
usually introduce the fuel at a single fixed rate during the on periods and
this rate should be sufficient to carry the gross or maximum design load.
In the case of coal stokers, which are usually capable of variable rates of
firing, it is desirable to operate at as low a rate as weather conditions will
permit, but the maximum firing rate of the stoker should be sufficient
to carry the gross load. This rate may be determined by the same method
as used for oil or gas.
In the case of warm air heating installations the heat loss of the building
expressed in Btu per hour can be determined by use of the Standard
Codes6 of the National Warm Air Heating and Air Conditioning Asso-
ciation. If the design heat loss of the building is divided by the proper
factor, the required gross output may be obtained from the proper charts
shown in Figs. 4, 5 and 6.
Example 8.^ The estimated net load (including domestic hot water supply) as calcu-
lated for a residence is 1500 sq ft of hot water radiation. Determine the firing rates for
various fuels assuming an overall efficiency of 70 per cent ; using coal with a calorific value
of 12,500 Btu per pound; No. 3 fuel oil and natural gas having a gross heating value of
1000 Btu per cubic foot.
Solution. Referring to Fig. 3, Chapter 13, a piping and pick-up factor for a net load of
1500 sq ft is found to be 43 per cent or the gross output is equivalent to 1500 X 1.43 =
2145 sq ft hot water radiation.
Using the chart in Figs. 4, 5 and 6 project vertically from the gross output value on
the proper horizontal scale to the intersection of the 70 per cent efficiency line. From the
intersection of this line proceed horizontally to the proper vertical scale where a direct
value of the required fuel burning rate is given. These values are rates of burning while
firing device is in operation and are not indicative of hourly fuel consumption.
By use of the respective charts the firing rates for the various fuels will be found to be:
coal 36.8 Ib per hour, oil 3.2 gal per hour, and gas 460 cu ft per hour.
TABLE 4. BUILDING LOAD FACTORS AND DEMANDS OF SOME DETROIT BUILDINGS'*
BUILDING CLASSIFICATION
LOAD FACTOR
LB or DEMAND PER HR
PER SQ FT OF EQUIVALENT
INSTALLED RADIATOR SURFACE
Clubs and Lodges
0 318
0 184
Hotels
0 316
0 907
Printing
0 287
0 217
Offices
0 263
0 209
Apartments
0 255
0 2^5
Retail Stores
0 238
0 182
Auto Sales and Service.—
0.223
0 248
Banks
0 203
0 158
Churches.
0 158
0 152
Department Stores
0.138
0 145
Theatres
0 126
0151
>Loc. Cit. Note 5.
8 P% Installation of Gravity Warm Air Heating Systems in Residences
edition) and the. Technical Code for the Design and Installation of Mechanical Warm Air Heating
systems, may be obtained from the National Warm Air Heating and Air Conditioning Association, 50 W.
Broad St., Columbus, Ohio.
240
CHAPTER 12. HEAT AND FUEL UTILIZATION
MAXIMUM DEMANDS AND LOAD FACTORS
In one form of district heating rates, a portion of the charge is based
upon the maximum demand of the building. The maximum demand may
be measured in several different ways. It may be taken as the instan-
taneous peak or as the rate of use during any specified interval. One
method is to take the average of the three highest hours during the
winter. These figures are available for a number of buildings in Detroit,
as shown in Table 4.
These maximum demands were measured by an attachment on the
condensation meter and therefore represent the amounts of condensation
passed through the meter in the highest hours, rather than the true rate
at which steam is supplied. There might be slight differences in these
two quantities due to time lag and to storage of condensate in the system,
but wherever this has been investigated it has been found to be negligible.
The load factor of a building is the ratio of the average load to the
maximum load and is an index of the utilization habits. Thus, in Table 4,
the theatres, operating for short hours, have a load factor of 0.126 as
compared with the figure of 0.318 for clubs and lodges.
PROBLEMS IN PRACTICE
1 • What will be the cost per year of heating a building with gas, assuming that
the calculated hourly heat loss is 92,000 Btu based on 0 F, which includes
26,000 Btu for infiltration? The design temperatures are 0 F and 72 F. The
normal heating season is 210 days, and the average outside temperature during
the heating season is 36.4 F. The heating efficiency will be 75 per cent. The
heating plant will be thermostatically controlled, and a temperature of 55 F
will be maintained from 11 p.m. to 7 a.m. Assume that the price of gas is
7 cents per 100,000 Btu of fuel consumption, and disregard the loss of heat
through open windows and doors.
The average hourly temperature is
fc , (72 X 16) + (55 X 8) _ ^ p
The maximum hourly heat loss will be
H - 92,000 -
79,000 (66.3 - 36.4) X 24 X 210 00. . ,,,,,,,. , Dj.
= 22046 hundred thousand Btu'
100.000 X 0.75 X (72-0)
2204.6 X 0.07 = $154.34 = cost per year of heating the building.
2 • What factors should be taken into consideration when determining the
efficiency at which a fuel will be burned?
Manufacturers' catalogs usually give equipment efficiencies obtained under test con-
ditions. These values do not allow for poor attendance, defects in installation, or poor
draft. Such efficiencies do not consider heat radiated from the outside of the equipment,
but in many cases this heat is utilized.
241
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
3 • If 20 tons of coal having a calorific value of 13,000 Btu per pound are burned
in a warm air furnace and produce 236,000,000 Btu at the bonnet, what is the
efficiency of the furnace?
_ Number of Btu at bonnet _ _ ffi .
Number of tons X calorific value X number of pounds in one ton ~~ e Clency-
286,000,000 X 100 _ „
20 X 13,000 X 2000 " 65 per cent-
4 • Make a rough approximation of the gas required to heat a building located
in Chicago, 111., assuming that the calculated heating surface requirements
are 1000 sq ft of hot water radiation based on design temperatures of 0 F and
70 F. Chicago has 800-Btu mixed gas, and 6315 degree-days.
Using Fig. 3, the fuel consumption for a design temperature of 0 F with 800-Btu gas is
found to be 0.08 cu ft of gas per degree-day per square foot of hot water radiation.
0.08 X 6315 X 1000 = 505,200 cu ft.
5 • A certain building has a maximum heat loss of 250,000 Btu per hour in — 15 F
weather. How many tons of fuel will be required to maintain a temperature of
70 F during a 260-day heating season in which the average temperature is 39 F?
The heating value of the fuel is 13,200 Btu per pound and the efficiency of com-
bustion is 60 per cent.
250,000 (70 - 39) 260 X 24
(70 + 15) 13,200 X 0.60 X 2000
tons'
6 • Which item may be determined more closely, the heating value of a fuel or
the efficiency of its combustion?
The^ heating values of oil, gas, and solid fuels are closely determinable, whereas the
efficiency of burning depends on the particular equipment chosen and the skill used in
handling it.
7 • In an office building, the thermostats are set to maintain 70 F from 7 a.m.
to 5 p.m. and 50 F during the rest of the time. When the outside temperature
is 30 F, how much saving might be expected because the temperatures are
lowered? Under the above conditions the building becomes 50 F by 11 p.m. and
warms up to 70 F by 8 a.m.
A temperature of 70 F is maintained during 9 hours, and one of 50 F during 8 hours; the
temperature would average about 60 F during the 7 hours required for cooling down and
warming up. The average is 60.4 for the 24 hours. (The average temperature calcu-
lated would have been 58.3 F, had the warming and cooling periods been neglected.)
The saving is 1 X 100 = x 100 - 24 per cent.
8 • How does the heat capacity of a structure influence the saving made by
carrying lower temperatures during the night?
The heat storage capacity of the walls prevents rapid dropingof temperatures at night-
time and delays the warming up process in the morning. In an extreme case, the building
would not reach the lowered temperature by the time the higher temperature is called
for in the morning. But under any conditions, the saving made by lowering the tem-
perature can be correctly estimated by using the average temperature observed over the
24-hour period as a factor, as in Question 7.
9 • What are some of the miscellaneous factors that may cause actual fuel
consumption to vary from the theoretical fuel requirements as calculated by
the use of heat losses, temperature difference, and fuel burning efficiency?
The opening of windows; abnormally high or low inside temperatures; other sources of
heat, such as machinery or lights; sun effect; high occupancy; and unusual winds.
242
Chapter 13
HEATING BOILERS
Cast-iron Boilers, Steel Boilers, Special Heating Boilers,
Gas-Fired Boilers, Hot Water Supply Boilers, Furnace Design,
Heating Surface, Testing and Rating Codes, Output Effic-
iency, Selection of Boilers, Connections and Fittings, Erection,
Operation and Maintenance, Boiler Insulation
STEAM and hot water boilers for low pressure heating work are built in
a wide variety of types, many of which are illustrated in the Catalog
Data Section, and are classified as (1) cast-iron sectional, (2) steel fire
tube, (3) steel water tube, and (4) special.
CAST-IRON BOILERS
Cast-iron boilers may be of round pattern with circular grate and hori-
zontal pancake sections joined by push nipples and tie rods, or of rec-
tangular pattern with vertical sections. The latter type may be either of
outside header construction where each section is independent of the other
and the water and steam connections are made externally through these
headers, or assembled with push nipples and tie rods, in which case the
water and steam connections are internal.
Cast-iron boilers usually are shipped knocked down to facilitate hand-
ling at the place of installation where assembly is made. One of the chief
advantages of cast-iron boilers is that the separate sections can be taken
into or out of basements and other places more or less inaccessible after
the building is constructed. This feature is of importance in making
repairs to or replacing a damaged or worn-out boiler and should be given
consideration in the original selection. Sufficient space should be pro-
vided in the boiler room for assembling the boiler and for disassembling it
conveniently if repairs are needed. With the outside header type of boiler
a damaged section in the middle of the boiler can be removed without
disturbing the other sections so side clearance should be provided.
Capacities of cast-iron boilers range from that required for small
residences up to about 18,000 sq ft of steam radiation. For larger loads,
cast-iron boilers must be installed in multiple, or a steel boiler must be
used. In most cases cast-iron boilers are limited to working pressures of
15 Ib for steam and 30 Ib for water. Special types are built for hot water
supply which will withstand higher local water pressures.
STEEL BOILERS
Two general classifications may be applied to steel boilers: first, with
regard to the relative position of water and hot gases, distinguished as fire
tube or water tube; second, with regard to arrangement of furnace and
243
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
flues, as (1) horizontal return tubular (HRT) boilers, (2) portable (self-
contained) firebox boilers with either water or fire tubes, and (3) water
tube boilers of the power type.
Fire tube boilers are constructed so that the water available to produce
steam is contained in comparatively large bodies distributed outside of the
boiler tubes, the hot gases passing within the tubes. In water tube boilers,
the water is circulated within the boiler tubes, heat being applied ex-
ternally to them.
The HRT boiler is the oldest type and consists of a horizontal cylin-
drical shell with fire tubes, enclosed in brickwork to form the furnace and
TABLE 1. PRACTICAL COMBUSTION RATES FOR SMALL COAL-FIRED HEATING BOILERS
OPERATING ON NATURAL DRAFT OF FROM y% IN. TO y% IN. WATER*
KIND OP COAL
SQ FT GRATE
LB or COAL PER SQ FT
GRATE PER HOUR
No. 1 Buckwheat Anthracite
Up to 4
5 to 9
10 to 14
15 to 19
20 to 25
3
3H
4
&A
5
Anthracite Pea
Up to 9
10 to 19
20 to 25
5
5Ji
6
Anthracite Nut and Larger
Up to 4
5 to 9
10 to 14
15 to 19
20 to 25
8
9
10
11
13
Bituminous
Up to 4
5 to 14
15 and above
9.5
12
15.5
aSteel boilers usually have higher combustion rates for grate areas exceeding 15 sq ft than those indicated
in this table.
combustion chamber. All heating surfaces and the interior of the boiler
are accessible for both cleaning and inspection. Horizontal return tubular
boilers, especially the larger sizes, should be suspended from structural
columns and beams independent of the brick setting. Small HRT boilers
sometimes are supported by brackets resting on the brick setting.
Portable firebox boilers are the more generally used type of steel heating
boilers, their outstanding characteristic being the water- jacketed firebox
which eliminates virtually all brickwork. They are shipped in one piece
from the factory and come to the job ready for immediate hook-up to
piping. They may be of welded or riveted construction and have either
water or fire tubes. Manufacturers' catalogs usually list heating surface
as well as grate area. The elimination of brickwork also makes this type
the most compact of steel boilers as well as the lowest in first cost.
Water tube boilers. For large heating loads water tube boilers are quite
frequently used. They usually require more head room than other types
of boilers but require considerably less floor space and make possible a
244
CHAPTER 13. HEATING BOILERS
much higher rate of evaporation per square foot of heating surface, with
proper setting, baffling and draft. Water tube boilers used for heating
purposes are either completely supported, insulated and encased in steel,
or else brick set, supported on structural steel columns and have the brick
setting encased in an insulated steel housing to prevent air infiltration and
to minimize heat losses. For large heating loads at a high rate of evapora-
tion, such boilers should be operated at pressures above 15 Ib per square
inch with a pressure-reducing valve on the connection to the heating main.
SPECIAL HEATING BOILERS
A special type of boiler, known as the magazine feed boiler, has been
developed for the burning of small sizes of anthracite and coke. These
are built of both cast-iron and steel, and have a large fuel carrying
capacity which results in longer firing periods than would be the case with
the standard types using buckwheat sizes of coal. Special attention must be
given to insure adequate draft and proper chimney sizes and connections.
Oil-burner boiler units, in which a special boiler has been designed with
a furnace shaped to meet the general requirements of oil burners or are
specially adapted to one particular burner have been developed by a
number of manufacturers. These usually are compact units with the
burner and all controls enclosed within an insulated steel jacket. Ample
furnace volume is provided for efficient combustion, and the heating
surfaces are proportioned for effective heat transfer. Consequently,
higher efficiencies are obtainable than with the ordinary coal fired boiler
converted to oil firing.
GAS-FIRED BOILERS
Gas boilers have assumed a well-defined individuality. The usual boiler
is sectional in construction with a number of independent burners placed
beneath the sections. In most boilers each section has its own burner. In
all cases the sections are placed quite closely together, much closer than
would be possible when burning a soot-forming fuel. The effort of the
designer is always to break the hot gas up into thin streams, so that all
particles of the heat-carrying gases can come as close as possible to the
heat-absorbing surfaces. Because there is no fuel bed resistance and because
the gas company supplies the motive power to draw in the air necessary
for combustion (in the form of the initial gas pressure) , draft losses through
gas boilers are low. See Chapter 11.
HOT WATER SUPPLY BOILERS
Boilers for hot water supply are classified as direct, if the water heated
passes through the boiler, and as indirect, if the water heated does not
come in contact with the water or steam in the boiler.
Direct heaters are built to operate at the pressures found in city supply
mains and are tested at pressures from 200 to 300 Ib per square inch.
The life of direct heaters depends almost entirely on the scale-making
properties of the water supplied. If water temperatures are maintained
below 140 F the life of the heater will be much longer than if higher
temperatures are used, owing to decreased scale formation and minimized
corrosion below 140 F. Direct water heaters in some cases are designed
to burn refuse and garbage.
245
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
Indirect heaters generally consist of steam boilers in connection with
heat exchangers of the coil or tube types which transmit the heat from the
steam to the water. This type of installation has the following advantages :
1. The boiler operates at low pressure.
2. The boiler is protected from scale and corrosion.
3. The scale is formed in the heat exchanger in which the parts to which the scale
is attached can be cleaned or replaced. The accumulation of scale does not affect
efficiency although it will affect the capacity of the heat exchanger.
4. Discoloration of water may be prevented if the water supply comes in contact
with only non-ferrous metal.
Where a steam heating system is installed, the domestic hot water
usually is obtained from an indirect heater placed below the water line of
the boiler.
FURNACE DESIGN
Good efficiency and proper boiler performance are dependent on cor-
rect furnace design embodying sufficient volume for burning the par-
ticular fuel at hand, which requires thorough mixing of air and gases at
a high temperature with a velocity low enough to permit complete com-
bustion of all the volatiles. On account of the small ampunt of volatiles
contained in coke, anthracite, and semi-bituminous coal, these fuels can
be burned efficiently with less furnace volume than is required for bi-
tuminous coal, the combustion space being proportioned according to the
amount of volatiles present.
Combustion should take place before the gases are cooled by the boiler
heating surface, and the volume of the furnace must be sufficient for this
purpose. The furnace temperature must be maintained sufficiently high
to produce complete combustion, thus resulting in a higher CO* content
and the absence of CO. Hydrocarbon gases ignite at temperatures
varying from 1000 to 1500 F.
The question of furnace proportions, particularly in regard to mechani-
cal stoker installations, has been given some consideration by various
manufacturers' associations. 'Arbitrary values have been recommended
for minimum dimensions. A customary rule-of -thumb method of figuring
furnace volumes is to allow 1 cu ft of space for a maximum heat release
of 50,000 Btu per hour. This value is equivalent to allowing approxi-
mately 1 cu ft for each developed horsepower, and it is approved by
most smoke prevention organizations.
The setting height will vary with the type of stoker. In an overfeed
stoker, for instance, all the volatiles must be burned in the combustion
chamber and, therefore, a greater distance should be allowed than for an
underfeed stoker where a considerable portion of the gas is burned while
passing through the incandescent fuel bed. The design of the boiler also
may affect the setting height, since in certain types the gas enters the
tubes immediately after leaving the combustion chamber, while in others
it passes ^over a bridge wall and toward the rear, thus giving a better
opportunity for combustion by obtaining a longer travel before entering
the tubes.
_ To secure ^suitable furnace volume, especially for mechanical stokers or
oil burners, it often is necessary either to pit the stoker or oil burner, or
246
CHAPTER 13. HEATING BOILERS
where water line conditions and headroom permit, to raise the boiler on a
brick foundation setting.
Smokeless combustion of the more volatile bituminous coals is furthered
by the use of mechanical stokers. (See Chapter 11.) Smokeless com-
bustion in hand-fired boilers burning high volatile solid fuel is aided (1)
by the use of double grates with down-draft through the upper grate, (2)
by the use of a curtain section through which preheated auxiliary air is
introduced over the fire toward the rear of the boiler, and (3) by the intro-
duction of preheated air through passages at the front of the boiler. All
three methods depend largely on mixing secondary air with the partially
burned volatiles and causing this mixture to pass over an incandescent
fuel bed, thus tending to secure more complete combustion than is pos-
sible in boilers without such provision.
HEATING SURFACE
Boiler heating surface is that portion of the surface of the heat transfer
apparatus in contact with the fluid being heated on one side and the gas or
refractory being cooled on the other side. Heating surface on which the
fire shines is known as direct or radiant surface and that in contact with
hot gases only, as indirect or convection surface. The amount of heating
surface, its distribution and the temperatures on either side thereof
influence the capacity of any boiler.
Direct heating surface is more valuable than indirect per square foot
because it is subjected to a higher temperature and also, in the case of
solid fuel, because it is in position to receive the full radiant energy of the
fuel bed. The heat transfer capacity of a radiant heating surface may be
as high as 6 to 8 times that of an indirect surface. This is one of the
reasons why the water legs of some boilers have been extended, especially
in the case of stoker firing where the extra amount of combustion chamber
secured by an extension of the water legs is important. For the same
reason, care should be exercised in building a refractory combustion
chamber in an oil-burning boiler so as not to screen any more of this
valuable surface with refractories than is necessary for good combustion.
The effectiveness of the heating surface depends on its cleanliness, its
location in the boiler, and the shape of the gas passages. Investigations1
by the U. S. Bureau of Mines show that:
1. A boiler in which the heating surface is arranged to give long gas passages of small
cross-section will be more efficient than a boiler in which the gas passages are short and of
larger cross-section.
2. The efficiency of a water tube boiler increases as the free area between individual
tubes decreases and as the length of the gas pass increases.
3. By inserting baffles so that the heating surface is arranged in series with respect to
the gas flow, the boiler efficiency will be increased.
The area of the gas passages must not be so small as to cause excessive
resistance to the flow of gases where natural draft is employed.
Heat Transfer Rates
Practical rates of heat transfer in heating boilers will average about
3300 Btu per sq ft per hour for hand-fired boilers and 4000 Btu per sq ft
"See U. 5. Bureau of Mines Bulletin No. 18, The Transmission of Heat into Steam Boilers.
247
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
per hour for mechanically fired boilers when operating at design load.
When operating at maximum load2 these values will run between 5000 and
6000 Btu per sq ft per hour. Boilers operating under favorable conditions
at the above heat transfer rates will give exit gas temperatures that are
considered consistent with good practice.
TESTING AND RATING CODES
The Society has adopted three solid fuel testing codes, a solid fuel
rating code and an oil fuel testing code. A.S.H.V.E. Standard and Short
Form Heat Balance Codes for Testing Low-Pressure Steam Heating
Solid Fuel Boilers — Codes 1 and 2 — (Revision of June 1929)8, are intended
to provide a method for conducting and reporting tests to determine heat
efficiency and performance characteristics. A.S.H.V.E. Performance
Test Code for Steam Heating Solid Fuel Boilers— Code No. 3 — (Edition of
1929)8 is intended for use with A.S.H.V.E. Code for Rating Steam Heating
Solid Fuel Hand-Fired Boilers4. The object of this test code is to specify
the tests to be conducted and to provide a method for conducting and
reporting tests to determine the efficiencies and performance of the boiler.
The A.S.H.V.E. Standard Code for Testing Steam Heating Boilers
Burning Oil Fuel5 is intended to provide a standard method for con-
ducting and reporting tests to determine the heating efficiency and per-
formance characteristics when oil fuel is used with steam heating boilers.
Steel Heating Boilers Ratings
The Steel Heating Boiler Institute has adopted a method for the rating of
low pressure boilers based on their physical characteristics and expressed
in square feet of steam or water radiation or in Btu per hour as given in
Table 2. The following requirements are included in this Code:
1. One square foot of steam radiation is to be considered equal to the emission of
240 Btu per hour and one square foot of water radiation is to be considered equal to
emission of 150 Btu per hour.
2. The rating of a boiler expressed in square feet of steam radiation in which solid fuel
hand fired is used is based on the amount equal to 14 times the heating surface of the
boiler in square feet.
3. The rating of a boiler expressed in square feet of steam radiation in which solid fuel
mechanically fired, or in which oil or gas is burned, is based on the amount equal to
17 times the heating surface of the boiler in square feet.
4. Heating surface is to be expressed in square feet and include those surfaces in the
boiler which are exposed to the products of combustion on one side and water on the
other. In measuring surfaces, the outer tube areas are to be considered. When a
boiler has the water leg height increased the heating surface noted in the published
ratings are not to be increased.
5. A grate area is to be considered as an area of the grate surface expressed in square
feet and measured in the plane of the top surface of the grate. For double grate boilers
the grate surface is to be considered as the area of the upper grate plus one-quarter of the
area of the lower grate.
6. The grate area of a boiler for rating as determined in No. 2 is to be not less than
that determined by the following formulae:
For boilers with ratings 1800 sq ft to 4000 sq ft of steam radiation:
Grate Area = ^/Catalogue Rating (in square feet steam radiation) — 200 Q\
^/
M
aFor definitions of design load and maximum load see pages 251 and 252.
'See A.S.H.V.E. TRANSACTIONS, Vol. 35, 1929, p. 12. Also Chapter 45.
4See A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 35. Also Chapter 45.
*See A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 23* Also Chapter 45.
24S
CHAPTER 13. HEATING BOILERS
TABLE 2. STANDARD STEEL HEATING BOILER RATINGS'*
HAND FIRED CAPACITY RATING
MECHANICALLY FIRED CAPACITY RATING
Steam
Radiation
SqFt
Water
Radiation
SqFt
Btu per Hr
Heating
Surface
SqFt
Grate
Area
SqFt
Steam
Radiation
SqFt
w . : Furnace Volume
Rg&j Btu^rHr *££-&*
^Ft : CuFt
1,800
2,880
432,000
129
7.9 ' 2,190 ! 3,500 , 525,600 , 15.7
2,200
3,520
528,000
158
8.9 2,680
4,280 j 643,200 19.2
2,600
4,160
624,000
186
9.7
3,160 5,050 ! 75S,400 , 22.6
3,000
4,800
720,000
215
10.5 3,650 5,840 876.000 26.1
3,500
5,600
840,000
250
11.4 , 4,250 6,800 1,020,000 30.4
4,000
6,400
960,000
286
12.2 j 4,860 7,770 ; 1,166,400 34.8
4,500
7,200
1,080,000
322
13.4
5,470 ! 8,750 1,312,800 39.1
5,000
8,000
1,200,000
358
14.5
6,080 : 9,720 i 1,459,200 43.5
6,000
9,600
1,440,000
429
16.4
7,290
11,660 1,749,600
52.1
7,000
11,200
1,680,000
500
18.1
8,500 13,600 i 2,040,000 60.8
8,500
13,600
2,OW,000
608
20.5
10,330
16,520 2,479,200
73.8
10,000
16,000
2,400,000
715
22.5
12,150 19,440
2,916.000
86.8
12,500
20,000
3,000,000
893
25.6
15,180 24,280
3,643,200
108.5
15,000
24,000
3,600,000
1,072
28.4
18,220
29,150 i 4,372,800
130.2
17,500
28,000
4,200,000
1,250
30.9
21,250
34,000
5T100,000
151.8
20,000
32,000
4,800,000
1,429
33.2
24,290
38,860
5,829,600
173.5
25,000
40,000
6,000,000
1,786
37.4
30,360
48,570
7,286,400
216.9
30,000
48,000
7,200,000
2,143
41.2
36,430
58,280
8,743,200
260.3
35,000
56,000
8,400,000
2,500
44.7
42,500
68,000
10,200,000
303.6
aAdopted by the Steel Heating Boiler Institute in cooperation with the Bureau of Standards, United States
Department of Commerce Simplified Practice Recommendation R 157-S5.
For boilers with ratings 4000 sq ft of steam radiation and larger:
Grate Area
V Catalogue Rating (in square feet steam radiation) — 1500
16.8
7. The volume for furnaces in which solid fuel is burned is to be considered as the
cubical content of the space between the bottom of the fuel bed and the first plane of
entry into or between the tubes. Volume of furnaces in which pulverized liquid fuel or
gaseous fuel is burned are to be considered as the cubical content of the space between
the hearth and the first plane of entry into or between the tubes. No minimum furnace
volume is to be specified for mechanical fired boilers burning anthracite.
8. The furnace volume for a boiler, with a rating as determined in No. 3 in^which oil,
gas or bituminous coal stoker fired is burned is not to be less than one cubic foot for
every 140 sq ft of steam rating.
9. The average height of furnace for the rating determined in No. 3 in which bitu-
minous coal, stoker fired is burned is not to be less than that determined graphically in
Fig. 1 or mathematically by the following formula:
(3)
where
H — average furnace height, inches as determined by the following formula;
12F 12F
H
WL
R = stoker fired boiler rating, square foot steam radiation.
A = plan area of firebox, square feet measured at the bottom of the fuel bed.
F = furnace volume, cubic feet.
249
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
W = average width of furnace, measured at the bottom of the fuel bed, feet.
L — length of furnace, feet. If the furnace is longer than the fuel bed or contains a
bridge wall, the total length of the furnace may be used except that this length
is not to exceed 2 J£ W.
BOILER OUTPUT
Boiler output as defined in A.S.H.V.E. Performance Test Code for
Steam Heating Solid Fuel Boilers (Code No. 3) is the quantity of heat
available at the boiler nozzle with the boiler normally insulated. It
should be based on actual tests conducted in accordance with this code.
This output is usually stated in Btu and in square feet of equivalent heat-
ing surface (radiation). According to the A.S.H.V.E. Standard Code for
PLAN AREA OF FURNACE, SQUARE FEET
FIG. 1. FURNACE HEIGHTS FOR STOKER FIRED BOILERS AND BITUMINOUS COAL
RATED IN SQUARE FEET STEAM RADIATION
Rating Steam Heating, Solid Fuel, Hand-Fired Boilers, the performance
data should be given in tabular or curve form on the following items for at
least five outputs ranging from maximum down to 35 per cent of maxi-
mum: (1) fuel available, (2) combustion rate, (3) efficiency, (4) draft
tension, (5) flue gas temperature. The only definite restriction placed on
setting the maximum output is that priming shall not exceed 2 per cent.
These curves provide complete data regarding the performance of the
boiler under test conditions. Certain other pertinent information, such as
grate area, heating surface and chimney dimensions is desirable also in
forming an opinion of how the boiler will perform in actual service.
The output of large heating boilers is frequently stated in terms of
boiler horsepower instead of in Btu per hour or square feet of equivalent
radiation.
250
CHAPTER 13. HEATING BOILERS
Boiler Horsepower : The evaporation of 34.5 Ib of water per hour
from and at 212 F which is equivalent to a heat output of 970.2 X 34.5 =
33,471.9 Btu per hour.
Equivalent Evaporation : The amount of water a boiler would
evaporate, in pounds per hour, if it received feed water at 212 F and
vaporized it at this same temperature and at atmospheric pressure.
It is usually considered that 10 sq ft of boiler heating surface will pro-
duce a rated boiler horsepower. A rated boiler horsepower in turn
can carry a design load of from 100 to 140 sq ft of equivalent radiation.
It is apparent, therefore, that 1 sq ft of boiler heating surface can carry a
design load of from 10 to 14 sq ft of equivalent radiation, or somewhat
more if the boiler is forced above rating. The application of these values
is discussed under the heading Selection of Boilers.
BOILER EFFICIENCY
The term efficiency as used for guarantees of boiler performance is
usually construed as follows:
1. Solid Fuels. The efficiency of the boiler alone is the ratio of the heat absorbed by
the water and steam in the boiler per pound of combustible burned on the grate to the
calorific value of 1 Ib of combustible as fired. The combined, efficiency of boiler, furnace
and grate is the ratio of the heat absorbed by the water and steam in the boiler per pound
of fuel as fired to the calorific value of 1 Ib of fuel as fired.
2. Liquid Fuels. The combined efficiency of boiler, furnace and burner is the ratio of
the heat absorbed by the water and steam in the boiler per pound of fuel to the calorific
value of 1 Ib of fuel.
Solid fuel boilers usually show an efficiency of 50 to 75 per cent when
operated under favorable conditions at their rated capacities. Infor-
mation on the combined efficiencies of boiler, furnace and burner has
resulted from research conducted at Yale University in cooperation with
the A.S.H.V.E, Research Laboratory and the American Oil Burner
Association*.
SELECTION OF BOILERS
Estimated Design Load : The load, stated in Btu per hour or equiva-
lent direct radiation, as estimated by the purchaser for the conditions of
inside and outside temperature for which the amount of installed radiation
was determined is the sum of the heat emission of the radiation to be
actually installed plus the allowance for the heat loss of the connecting
piping plus the heat requirement for any apparatus requiring heat con-
nected with the system (A.S.H.V.E. Standard Code for Rating Steam
Heating Solid Fuel Hand-Fired Boilers— Edition of April, 1932).
The estimated design load is the sum of the following three items7:
1. The estimated heat emission in Btu per hour of the connected radiation (direct,
indirect or central fan) to be installed.
2. The estimated maximum heat in Btu per hour required to supply water heaters
or other apparatus to be connected to the boiler.
6Study of the Characteristics of Oil Burners and Heating Boilers, by L. E. Seeley and E. J. Tavanlar
(A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 517), A Study of Intermittent Operation of Oil Burners, by L.
E. Seeley and J. H. Powers (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 317).
7A.S.H.V.E. Code of Minimum Requirements for the Heating and Ventilation of Buildings (Edition
of 1929).
251
HEATING VENTILATING Am CONDITIONING GUIDE 1938
3. The estimated heat emission in Btu per hour of the piping connecting the radiation
and other apparatus to the boiler.
Estimated Maximum Load : Construed to mean the load stated in
Btu per hour or the equivalent direct radiation that has been estimated by
the purchaser to be the greatest or maximum load that the boiler will be
called upon to carry. (A.S.H.V.E. Standard Code for Rating Steam
Heating Solid Fuel Hand-Fired Boilers— Edition of April, 1932.)
The estimated maximum load is given by8:
4. The estimated increase in the normal load in Btu per hour due to starting up cold
radiation. This percentage of increase is to be based on the sum of Items 1, 2 and 3
and the heating-up factors given in Table 3.
TABLE 3. WARMING-UP ALLOWANCES FOR Low PRESSURE STEAM AND
HOT WATER HEATING BoiLERsai bi c
DESIGN LOAD (REPRESENTING STJMMA/TION OF ITEMS 1, 2, AND 3,d
PESCENTAOE CAPACITY TO ADD
FOR WABMINO UP
Btu per Hour
Equivalent Square Feet of Radiation*
Up to 100,000
100,000 to 200,000
200,000 to 600,000
600,000 to 1,200,000
1,200,000 to 1,800,000
Above 1,800,000
Up to 420
420 to 840
840 to 2500
2500 to 5000
5000 to 7500
Above 7500
65
60
55
50
45 .
40
aThis table is taken from the A.S.H.V.E. Code of Minimum Requirements for the Heating and Venti-
lation of Buildings, except that the second column has been added for convenience in interpreting the design
load in terms of equivalent square feet of radiation.
bSee also Time Analysis in Starting Heating Apparatus, by Ralph C. Taggert (A.S.H.V.E. TRANSAC-
TIONS, Vol. 19, 1913, p. 292); Report of A.S.H.V.E. Continuing Committee on Codes for Testing and Rating
Steam Heating Solid Fuel Boilers (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 35) ; Selecting the Right
Size Heating Boiler, by Sabin Crocker (Heating, Piping and Air Conditioning, March, 1932).
cThis table refers to hand-fired, solid fuel boilers. A factor of 20 per cent over design load is adequate
when automatically-fired fuels are used (see Fig. 3).
d240 Btu per square foot.
Other things to be considered are:
5. Efficiency with hard or soft coal, gas, or oil firing, as the case may be.
6. Grate area with hand-fired coal, or fuel burning rate with stokers, oil, or gas.
7. Combustion space in the furnace.
8. Type of heat liberation, whether continuous or intermittent, or a combination of
both.
9. Miscellaneous items consisting of draft available, character of attendance, pos-
sibility of future extension, possibility of breakdown and headroom in the boiler room.
Radiation Load
The connected radiation (Item 1) is determined by calculating the^heat
losses in accordance with data given in Chapters 5, 6 and 7, and dividing
by 240 to change to square feet of equivalent radiation as explained in
Chapter 14. For hot water, the emission commonly used is 150 Btu per
square foot, but the actual emission depends on the temperature of the
medium in the heating units and of the surrounding air. (See Chapter 14.)
Although it is customary to use the actual connected load in equivalent
square feet of radiation for selecting the size of boiler, this connected load
usually represents a reserve in heating capacity to provide for infiltration
in the various spaces of the building to be heated, which reserve, however,
8Loc. Cit. Note 7.
252
CHAPTER 13. HEATING BOILERS
is not in use at all places at the same time, or in any one place at all times.
For a further discussion of this subject see Chapter 6.
Hot Water Supply Load
When the hot water supply (Item 2) is heated by the building heating
boiler, this load must be taken into consideration in sizing the boiler. The
0.6 60
^0.3 § 5 |5|4.5
OK < |j
So-2 ^40 * 105 a
LI i.it
1000
3OOO
OUTPUT. SQ. FT, EQUIVALENT STEAM RADIATION (240 BTU PER 3Q. FT.)
BOILER DATA- CRATE AREA.SQ.FT. 16-0 FUEL-BITUMINOUS 3/4- LUMP
HEATING SURFACE.SQ FT. 254 ANALYSIS- VOLATILE MATTER 34.687.
WEIGHT, LB. 0160 FIXED CARBON 35-44
FUEL CAPACITY. LB. 63. ASH 9.97
FUEL AVAIL ABLE, LB. 414. SULPHUR 2.«6
. io
FIG 2 TYPICAL PERFORMANCE CURVES FOR A 36-iN. CAST-IRON SECTIONAL STEAM
HEATING BOILER, BASED ON THE A.S.H.V.E. CODE FOR RATING STEAM
HEATING SOLID FUEL HAND-FIRED BOILERS
allowance to be made will depend on the amount of water heated and its
temperature rise. A good approximation is to add 4 sq ft of equivalent
radiation for each gallon of water heated per hour through a temperature
range of 100 F. For more specific information, see Chapter 43.
Piping Tax (Item 3)
It is common practice to add a flat percentage allowance to the
equivalent connected radiation to provide for the heat loss from bare and
covered pipe in the supply and return lines. The use of a flat allowance of
25 per cent for steam systems and 35 per cent for hot water systems is
preferable to ignoring entirely the load due to heat loss from the supply
253
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
and return lines, but better practice, especially when there is much bare
pipe, is to compute the emission from both bare and covered pipe surface
in accordance with data in Chapter 39. A chart is shown in Fig. 3 indicat-
ing percentage allowances for piping and warming-up which are applic-
able to automatically-fired heating plants using steam radiation. With
direct radiation served by bare supply and return piping the percentages
may be higher than those stated, while in the case of unit heaters where
the output is concentrated in a few locations/ the piping tax may be
10 per cent or less.
10 12 14
NET LOAD, STEAM RADIATION, THOUSAND SQ FT
18
FIG. 3. PERCENTAGE ALLOWANCE FOR PIPING AND WARMING-UP
Warming-Up Allowance
The warming-up allowance represents the load due to heating the boiler
and contents to operating temperature and heating up cold radiation and
piping. (See Item 4.) The factors to be used for determining the
allowance to be made should be selected from Table 3 and should be
applied to the estimated design load as determined by Items 1, 2 and 3.
While in every case the estimated maximum load will exceed the design
load if adequate heating response is to be achieved, there is however, no
object in over-estimating the allowances, as the only effect would be to
reduce the time of warming-up by a few minutes. Otherwise, it might
result in firing the boiler unduly and increasing the cost of operation.
Performance Curves for Boiler Selection
In the selection of a boiler to meet the estimated load, the A.S.H.V.E.
Standard Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers
recommends the use of performance curves based on actual tests con-
ducted in accordance with the A.S.H.V.E. Performance Test Code for
Steam Heating Solid Fuel Boilers (Code No. 3), similar to the typical
curves shown in Fig. 2. It should be understood that performance data
apply to test conditions and that a reasonable allowance should be made
for decreased output resulting from soot deposit, poor fuel or inefficient
attention.
254
CHAPTER 13. HEATING BOILERS
Selection Based on Heating Surface and Grate Area
Where performance curves are not available, a good general rule for
conventionally-designed boilers is to provide 1 sq ft of boiler heating
surface for each 14 sq ft of equivalent radiation (240 Btu per square foot)
represented by the design load consisting of connected radiation, piping
tax and domestic water heating load. As stated in the section on Boiler
Output, this is equivalent to allowing 10 sq ft of boiler heating surface per
boiler horsepower. In this case it is assumed that the maximum load
including the warming-up allowance will be provided for by operating the
boiler in excess of the design load, that is, in excess of the 100 per cent
rating on a boiler-horsepower basis.
Due to the wide variation encountered in manufacturers' ratings for
boilers of approximately the same capacity, it is advisable to check the
grate area required for heating boilers burning solid fuel by means of the
following formula:
TT
G = CXFXE (4)
where
G = grate area, square feet.
H = required total heat output of the boiler, Btu per hour (see Selection of Boilers,
p. 251).
C — combustion rate in pounds of dry coal per square foot of grate area per hour,
depending on the kind of fuel and size of boiler as given in Table 1.
F — calorific value of fuel, Btu per pound.
E =• efficiency of boiler, usually taken as 0.60.
Example 1. Determine the grate area for a required heat output of the boiler of
500,000 Btu per hour, a combustion rate of 6 Ib per hour, a calorific value of 13,000 Btu
per pound, and an efficiency of 60 per cent.
The boiler selected should have a grate area not less than that deter-
mined by Formula 4. With small boilers where it is desired to provide
sufficient coal capacity for approximately an eight-hour firing period plus
a 20 per cent reserve for igniting a new charge, more grate area may be
required depending upon the depth of the fuel pot.
Selection of Steel Heating Boilers
Boiler ratings previously described under the Steel Heating Boiler
Institute's Boiler Rating Code are intended to correspond with the esti-
mated design load based on the sum of items 1, 2 and 3 outlined on pages
252 and 253. Insulated residence type boilers for oil or gas may carry
a net load expressed in square feet of steam radiation of not more than
17 times the square feet of heating surface in the boiler, provided the
boiler manufacturer guarantees the boiler to be capable of operating at a
maximum output of not less than 150 per cent of net load rating with over-
all efficiency of not less than 75 per cent with at least two different makes
of each type of standard commercial burner recommended by the boiler
manufacturer. If the heat loss from the piping system exceeds 20 per cent
of the installed radiation, the excess is to be considered as a part of the net
load.
255
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
When the estimated heat emission of the piping (connecting radiation,
and other apparatus to the boiler) is not known the net load to be con-
sidered for the boiler may be determined from Table 4.
Selection of Gas-Fired Boilers
Gas-heating appliances should be selected in accordance with the
percentage allowances given in Fig. 3. These factors are for thermo-
statically-controlled systems; in case manual operation is desired, a
warming-up allowance of 100 per cent is recommended by the A.G.A.
A gas boiler selected by the use of the A.G.A. factors will be the minimum
TABLE 4. BOILER RATINGS BASED ON NET LoADa
HAJTD FIRED RATINGS
MECHANICALLY FIRED RATINGS
Steam Radiation Sq Ft
Net Loadb
Steam Radiation Sq Ft
Steam Radiation Sq Ft
Net Loadb
Steam Radiation Sq Ft
1,800
1,389
2,190
1,695
2,200
1,702
2,680
2,089
2,600
2,020
3,160
2,461
3,000
2,335
3,650
2,853
3,500
2,732
4,250
3,335
4,000
3,135
4,860
3,830
4,500
3,540'
5,470
4,330
5,000
3,945
6,080
4,834
6,000
4,770
7,290
5,850
7,000
5,608
8,500
6,885
8,500
6,885
10,330
8,490
10,000
8,197
12,150
10,125
12,500
10,417
15,180
12,650
15,000
12,500
18,220
15,183
17,500
14,584
21,250
17,708
20,000
16,667
24,290
20,242
25,000
20,834
30,360
25,300
30,000
25,000
36,430
30,359
35,000
29,167
42,500
35,417
aAdopted by the Steel Heating Boiler Institute in cooperation with the Bureau of Standards , United States
Department of Commerce Simplified Practice Recommendation R 157-35.
bThe net load is made up by the sum of the estimated design load, items 1 and 2 (pages 252 and 253). All
net loads are expressed in 70 F. For hand fired boiler ratings less than 1800 sq ft of steam or 2880 sq. ft of
water and mechanically fired boiler ratings of 2190 sq ft of steam or 3500 sq ft of water, apply the factor
1.3 to the net load to determine the boiler size. For water boilers use the equivalent net load for steam
boilers of similar physical size.
size boiler which can carry the load. From a fuel economy standpoint, it
may be advisable to select a somewhat larger boiler and then throttle the
gas and air adjustments as required. This will tend to give a low stack
temperature with high efficiency and at the same time provide reserve
capacity in case the load is under-estimated or more is added in the future.
Conversions
The conversion of a coal or oil boiler to gas burning is simpler than the
reverse since little furnace volume need be provided for the proper com-
bustion of gas. When a solid fuel boiler of 500 sq ft (or less) capacity is
converted to gas burning, the necessary gas heat units should be approxi-
mately double the connected load. The presumption for a conversion
job is that the boiler is installed and probably will not be made larger;
256
CHAPTER 13. HEATING BOILERS
therefore, it is a matter of setting a gas-burning rate to obtain best results
with the available surface. Assuming a combustion efficiency of 75 per
cent for a conversion installation the boiler output would be 2 X 0.75
= 1.5 times the connected load, which allows 50 per cent for piping tax
and pickup. In converting large boilers, the determination of the re-
quired Btu input should not be done by an arbitrary figure or factor but
should be based on a detailed consideration of the requirements and
characteristics of the connected load.
An efficient conversion installation depends upon the proper size of
flue connection. Often the original smoke breeching between the boiler
and chimney is too large for gas firing, and in this case, flue orifices can be
used. They are discs provided with an opening of the size for the gas
input used in this boiler. The size should be based on 1 sq in. of flue area
for each 7500 hourly Btu input.
If dampers are found in the breeching they should be locked in position
so that they will not interfere with the normal operation of the gas burners
at maximum flow. In the case of large boiler conversions, automatic
damper regulators proportion the position of the flue dampers to the
amount of gas flowing and may be substituted for existing dampers.
Generally in residence conversions automatic dampers are not of the
proportioning type but close the flue during the off periods of the gas
burners. Automatic shutoff dampers should be located between the
backdraft diverter and the chimney flue. Automatic dampers are usually
designed to operate with electric contact mechanism, but frequently an
arrangement is utilized which functions with mechanical fluid or gas
pressure.
Physical Limitations
As it will usually be found that several boilers will meet the speci-
fications, the final selection of the boiler may be influenced by other con-
siderations, some of which are:
1. Dimensions of boiler.
2. Durability under service.
3. Convenience in firing and cleaning.
4. Adaptability to changes in fuel and kind of attention.
5. Height of water line.
In large installations, the use of several smaller boiler units instead of
one larger one will obtain greater flexibility and economy by permitting
the operation, at the best efficiency, of the required number of units
according to the heat requirements.
Space Limitations
Boiler rooms should, if possible, be situated at a central point with
respect to the building and should be designed for a maximum of natural
light. The space in front of the boilers should be sufficient for firing,
stoking, ash removal and cleaning or renewal of flues, and should be at
least 3 ft greater than the length of the boiler firebox.
A space of at least 3 ft should be allowed on at least one side of every
boiler for convenience of erection and for accessibility to the various
257
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
dampers, cleanouts and trimmings. The space at the rear of the boiler
should be ample for the chimney connection and for cleanouts. With
large boilers the rear clearance should be at least 3 ft in width.
The boiler room height should be sufficient for the location of boiler
accessories and for proper installation of piping. In general the ceiling
height for small steam boilers should be at least 3 ft above the normal
boiler water line. With vapor heating, especially, the height above the
boiler water line is of vital importance.
When steel boilers are used, space should be provided for the removal
and replacement of tubes.
CONNECTIONS AND FITTINGS
The velocity of flow through the outlets of low pressure steam heating
boilers should not exceed 15 to 25 fps if fluctuation of the water line and
undue entrainment of moisture are to be avoided. Steam or water outlet
connections preferably should be the full size of the manufacturers'
tapping and should extend vertically to the maximum height available
above the boiler. For gravity circulating steam heating systems, it is
recommended that a Hartford Loop, described in Chapter 16, be utilized
in making the return connection.
Particular attention should be given to fitting connections to secure con-
formity with the A.S.MJS. Boiler Construction Code for Low Pressure
Heating Boilers. Attention is called in particular to pressure gage piping,
water gage connections and safety valve capacity.
Steam gages should be fitted with a water seal and a shut-off consisting
of a cock with either a tee or lever handle which is parallel to the pipe
when the cock is open. Steam gage connections should be of copper or
brass when smaller than 1 in. I.P.S.9 if the gage is more than 5 ft from the
boiler connection, and also in any case where the connection is less than
M in. I.P.S.
Each steam or vapor boiler should have at least one water gage glass and
two or more gage cocks located within the range of the visible length of the
glass. The water gage fittings or gage cocks may be direct connected to
the boiler, if so located by the manufacturer, or may be mounted on a
separate water column. No connections, except. for combustion regu-
lators, drains or steam gages, should be placed on the pipes connecting
the water column and the boiler. If the water column or gage glass is con-
nected to the boiler by pipe and fittings, a cross, tee or equivalent, in which
a deanout plug or a drain valve and piping may be attached, should be
placed in the water connection at every right-angle turn to facilitate
cleaning. The water line in steam boilers should be carried at the level
specified by the boiler manufacturer.
Safety valves should be capable of discharging all the steam that can be
generated by the boiler without allowing the pressure to rise more than
5 Ib above the maximum allowable working pressure of the boiler. This
should be borne in mind particularly in the case of boilers equipped with
mechanical stokers or oil burners where the amount of grate area has
little significance as to the steam generating capacity of the boiler.
'A3.M.E. Code, Identification of Piping Systems.
258
CHAPTER 13. HEATING BOILERS
Where a return header is used on a cast-iron sectional boiler to distribute
the returns to both rear tappings, it is advisable to provide full size
plugged tees instead of elbows where the branch connections enter the
return tappings. This facilitates cleaning sludge from the bottom of the
boiler sections through the large plugged openings. An equivalent clean-
out plug should be provided in the case of a single return connection.
Blow-off or drain connections should be made near the boiler and so
arranged that the entire system may be drained of water by opening the
drain cock. In the case of two or more boilers separate blow-off connec-
tions must be provided for each boiler on the boiler side of the stop valve
on the main return connection.
Water service connections must be provided for both steam and water
boilers, for refilling and for the addition of make-up water to boilers. This
connection is usually of galvanized steel pipe, and is made to the return
main near the boiler or boilers.
For further data on pipe connections for steam and hot water heating
systems, see Chapters 16 and 17 and thtA.S.M.E. Boiler Construction
Code for Low Pressure Heating Boilers.
Smoke Breeching and Chimney Connections. The breeching or smoke
pipe from the boiler outlet to the chimney should be air- tight and as short
and direct as possible, preference being given to long radius and 45-deg
instead of 90-deg bends. The breeching entering a brick chimney should
not project beyond the flue lining and where practicable it should be
grouted from the inside of the chimney. A thimble or sleeve grout
usually is provided where the breeching enters a brick chimney.
Where a battery of boilers is connected into a breeching each boiler
should be provided with a tight damper. The breeching for a battery
of boilers should not be reduced in size as it goes to the more remote
boilers. Good connections made to a good chimney will usually result in
a rapid response by the boilers to demands for heat.
ERECTION, OPERATION, AND MAINTENANCE
The directions of the boiler manufacturer always should be read before
the assembly or installation of any boiler is started, even though the
contractor may be familiar with the boiler. All joints requiring boiler
putty or cement which cannot be reached after assembly is complete
must be finished as the assembly progresses.
The following precautions should be taken in all installations to prevent
damage to the boiler:
1. There should be provided proper and convenient drainage connections for use if
the boiler is not in operation during freezing weather.
2. Strains on the boiler due to movement of piping during expansion should ^ be
prevented by suitable anchoring of piping and by proper provision for pipe expansion
and contraction.
3. Direct impingement of too intense local heat upon any part of the boiler surface,
as with oil burners, should be avoided by protecting the surface with firebrick or other
refractory material.
4. Condensation must flow back to the boiler as rapidly and uniformly as possible.
Return connections should prevent the water from backing out of the boiler.
5. Automatic boiler feeders and low water cut-off devices which shut off the source
259
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
of heat if the water in the boiler falls below a safe level are recommended for boilers
mechanically fired.
Boiler Troubles
A complaint regarding boiler operation generally will be found to be
due to one of the following:
1. The boiler fails to deliver enough heat. The cause of this condition may be: (a) poor
draft; (&) poor fuel; (c) inferior attention or firing; (d) boiler too small; (e) improper
piping; (f) improper arrangement of sections; (g) heating surfaces covered with soot;
and (h) insufficient radiation installed.
2. The water line is unsteady. The cause of this condition may be: (a) grease and dirt
in boiler; (b) water column connected to a very active section and, therefore, not
showing actual water level in boiler; and (d) boiler operating at excessive output.
3. Water disappears from gage glass. This may be caused by: (a) priming due to
grease and dirt in boiler; (b) too great pressure difference between supply and return
piping preventing return of condensation; (c) valve closed in return line; (d) connection
of bottom of water column into a very active section or thin waterway; and (e) improper
connections between boilers in battery permitting boiler with excess pressure to push
returning condensation into boiler with lower pressure.
4. Water is carried over into steam main. This may be caused by: (a) grease and dirt
in boiler; (b) insufficient steam dome or too small steam liberating area; (c) outlet con-
nections of too small area; (d) excessive rate of output; and (e) water level carried
higher than specified.
5. Boiler is slow in response to operation of dampers. This may be due to: (a) poor
draft resulting from air leaks into chimney or breeching; (b) inferior fuel; (c) inferior
attention; (d) accumulation of clinker on grate; and (e) boiler too small for the load.
6. Boiler requires^ too frequent cleaning of flues. This may be due to: (a) poor draft;
(6) smoky combustion; (c) too low a rate of combustion; and (d) too much excess air
in firebox causing chilling of gases.
7. Boiler smokes through fire door. This may be due to: (a) defective draft in chimney
or incorrect setting of dampers; (b) air leaks into boiler or breeching; (c) gas outlet from
firebox plugged with fuel; (d) dirty or clogged flues; and (e) improper reduction in
breeching size.
Cleaning Steam Boilers
All boilers are provided with flue clean-out openings through which the
heating surface^ can be reached by means of brushes or scrapers. Flues
of solid fuel boilers should be cleaned often to keep the surfaces free of
soot or ash. Gas boiler flues and burners should be cleaned at least once
a year. Oil burning boiler flues should be examined periodically to deter-
mine when cleaning is necessary.
The grease used to lubricate the cutting tools during erection of new
piping systems serves as a carrier for sand and dirt, with the result that
a scum of fine particles and grease accumulates on the surface of the
water in all new boilers, while heavier particles may settle to the bottom
of the boiler and form sludge. These impurities have a tendency to cause
foaming, preventing the generation of steam and causing an unsteady
water line.
This unavoidable accumulation of oil and grease should be removed
by blowing off the boiler as follows: If not already provided, install a
surface blow connection of at least 1% in. nominal pipe size with outlet
extended to within 18 in. of the floor or to sewer, inserting a valve in line
close to boiler. Bring the water line to center of outlet, raise steam pres-
sure and while fire is burning briskly open valve in blow-off line. When
260
CHAPTER 13. HEATING BOILERS
pressure recedes close valve and repeat process adding water at intervals
to maintain proper level. As a final operation bring the pressure in the
boiler to about 10 Ib, close blow-off, draw the fire or stop burner, and open
drain valve. After boiler has cooled partly, fill and flush out several times
before filling it to proper water level for normal service. The use of soda,
or any alkali, vinegar or any acid is not recommended for cleaning heating
boilers because of the difficulty of complete removal and the possibility
of subsequent injury, after the cleaning process has been completed.
Insoluble compounds have been developed which are effective, but
special instructions on the proper cleaning compound and directions for
its use in a boiler, as given by the boiler manufacturer, should be carefully
followed.
It is common practice when starting new installations to discharge
heating returns to the sewer during the first week of operation. This
prevents the passage of grease, dirt or other foreign matter into the boiler
and consequently may avoid the necessity of cleaning the boiler. During
the time the returns are being passed to the sewer, the feed valve should
be cracked sufficiently to maintain the proper water level in the boiler.
Care of Idle Heating Boilers
Heating boilers are often seriously damaged during summer months
due chiefly to corrosion resulting from the combination of sulphur from
the fuel with the moisture in the cellar air. At the end of the heating
season the following precautions should be taken:
1. All heating surfaces should be cleaned thoroughly of soot, ash and residue, and the
heating surfaces of steel boilers should be given a coating of lubricating oil on the ore
side.
2. All machined surfaces should be coated with oil or grease.
3. Connections to the chimney should be cleaned and in case of small boilers the pipe
should be placed in a dry place after cleaning.
4. If there is much moisture in the boiler room, it is desirable to drain the boiler to
prevent atmospheric condensation on the heating surfaces of the boiler when they are
below the dew-point temperature. Due to the hazard of some one inadvertently building
a fire in a dry boiler, however, it is safer to keep the boiler filled with water. A hot water
system usually is left filled to the expansion tank.
5. The grates and ashpit should be cleaned.
6. Clean and repack the gage glass if necessary.
7. Remove any rust or other deposit from exposed surfaces by scraping with a wire
brush or sandpaper. After boiler is thoroughly cleaned, apply a coat of preservative
paint where required to external parts normally painted.
8. Inspect all accessories of the boiler carefully to see that they are in good working
order. In this connection, oil all door hinges, damper bearings and regulator parts.
BOILER INSULATION
Insulation for cast-iron boilers is of two general types: (1) plastic
material or blocks wired on, cemented and covered with canvas or duck;
and (2) blocks, sheets or plastic material covered with a metal jacket
furnished by the boiler manufacturer. Self-contained steel firebox boilers
usually are insulated with blocks, cement and canvas, or rock wool
blankets; HRT boilers are brick set and do not require insulation beyond
that provided in the setting. It is essential that the insulation on a boiler
261
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
and adjacent piping be of non-combustible material as even slow-burning
insulation constitutes a dangerous fire hazard in case of low water in
the boiler.
PROBLEMS IN PRACTICE
1 • What basic requirements of boiler design are to be accomplished with a
combination, boiler and oil burner unit?
Combination units vary widely but in general, the basic requirements of design depends
upon a combustion chamber of proper design and arranged for the flame shape with
adequate heating surface for the complete combustion of the fuel.
2 • What is the normal rating range of each type of boiler?
a. Cast-iron boilers are rated at from 200 to 18,000 sq ft EDR.
b. Steel boilers are rated at from 300 to 50,000 sq ft EDR.
3 • What factors contribute to economical fuel operation in low pressure
boilers burning coal or oil?
a. Proper furnace volume for complete combustion.
b. Arrangement of heating surfaces in series to create a turbulent and scrubbing contact
of gases against the convective surfaces.
c. Rapid internal water circulation which will remove steam bubbles from the water
side of heating surfaces and allow other steam bubbles to be formed. Rapid disen-
gagement of steam bubbles increases the steam generating efficiency of each unit
area of heating surface, and thereby lowers flue gas temperatures.
4 • What ecpiipment is usually directly attached to a low pressure heating
boiler?
For coal burning steam boilers: water column, water gage, tri-cocks, steam gage, lever
pop safety valve, boiler damper regulator.
For coal burning hot water boilers: damper regulator, altitude gage, thermometer, relief
valve.
For oil burning boilers, the damper regulators are omitted and the following additional
equipment is usually attached: automatic water feeder, low water cutout, a pressure
control, and a water temperature control. These are generally furnished by the oil
burner manufacturer and do not come with the boiler.
5 • What general precautions regarding the boiler should be taken to make
sure a proposed beating installation will work properly?
a. Select the right size and type of boiler.
&. Be sure the combustion space is proper for the type of fuel burned.
c. Allow sufficient space around the boiler for cleaning.
d. Secure proper height and area of chimney and connecting breeching.
e. Clean the boiler thoroughly and provide surface blowoff connections and bottom
blowoff connections for periodic cleaning after operation is begun.
/. See that the boiler heating surface is cleaned at regular periods.
g. Check flue gas temperatures and make a flue gas analysis at least once a month.
h. Secure information and advice from boiler manufacturer.
5 • What is the average heat transmission rate hi heating boilers hi Btu per
sq ft of beating surface per hour?
3500 for coal burning boilers; 4200 for oil burning boilers.
262
Chapter 14
RADIATORS AND GRAVITY CONVECTORS
Heat Emission of Radiators and Convectors, Types o£ Radi-
ators, Output of Radiators, Heating Effect, Heating Up the
Radiator and Convector, Enclosed Radiators, Convectors,
Selection, Code Tests, Gravity-Indirect Heating Systems
THE accepted terms for heating units are: (1) radiators, for direct
surface heating units, either exposed, enclosed, or shielded, which
emit a large percentage of their heat by radiation; and (2) connectors, for
heating units haying a large percentage of extended fin surface and which
emit heat principally by convection. Convectors are dependent upon
enclosures to provide the circulation by gravity of large volumes of air.
HEAT EMISSION OF RADIATORS AND CONVECTORS
All heating units emit heat by radiation and convection. The resultant
heat from these processes depends upon whether or not the heating unit is
exposed or enclosed and upon the contour and surface characteristics of
the material in the units.
An exposed radiator emits less than half of its heat by radiation, the
amount depending upon the size and number of sections. When the
radiator is enclosed or shielded, radiation is further reduced. The balance
of the emission is by conduction to the air in contact with the heating
surface, and the resulting circulation of the air warms by convection.
A convector emits practically all of its heat by conduction to the air
surrounding it and this heated air is in turn transmitted by convection to
the rooms or spaces to be wanned, the heat emitted by radiation being
negligible.
TYPES OF RADIATORS
Present day radiators may be classified as tubular, wall, or window
types, and are generally made of cast iron. Catalogs showing the many
designs and patterns available now include a junior size which is more
compact than the standard unit.
Pipe Coils
Pipe coils are assemblies of standard pipe or tubing (1 in. to 2 in.) which
are used as radiators. In older practice these coils were commonly used
in factory buildings, but now wall type radiators are most frequently used
for this service. When coils are used, the miter type assembly is to be
263
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
preferred as it best cares for expansion in the pipe. Cast manifolds or
headers, known as branch tees, are available for this construction.
OUTPUT OF RADIATORS
The output of a radiator can be measured only by the heat it emits.
The old standard of comparison used to be square feet of actual surface,
but since the advance in radiator design and proportions, the surface area
alone is not a true index of output. (The engineering unit of output is the
Mb or 1000 Btu.) However, during the period of transition from the old
to the new, radiators may be referred to in terms of equivalent square feet.
For steam service this is based on an emission of 240 Btu per hour per
square foot.
TABLE 1. VARIATION IN DIMENSIONS AND CATALOG RATINGS OF
10-SECTiON TUBULAR RADIATORS
No_«rfTuh««
3
4
5
6
7
Wiritfl of T^'ftt™- Tnp.hea
4.6-5.1
6.0-7.0
8.0-8.9
9.1-10.4
11.4-12 8
L$pgt)i p^f Sftfltirm ^it Inches
2.5
2.5
2.5
2.5
2.5-30
HEIGHT WITH LEGS— INCHES
HEJ
LT EMISSION—
EQUIVALENT S
QUA.RE FEET
13-14
20
25 0-32 5
16-18
28.5
30 0-38 3
20-21
22-23
25-26
30-32
36-38
15.0-17.5
20.0-21.3
20.0-26.7
25.0-30.9
30.0-36.7
20.0-22.5
25
25.0-27.5
33.3-35.0
40.0-42.5
25.0-31.2
30.0-33.9
32.5-39.8
40.0-48.6
50.0-56.5
30
35
37.5-40.0
50
60
36.7-45.0
40.0-45.2
50.0-53.5
63.3-62.5
70.0-75.4
Output of Tubular Radiators
^ Table 1 illustrates the difficulty in tabulating tubular radiator outputs
since there is so much variation in design between the products of the
different manufacturers. Only on the four-tube and six-tube sizes is there
any practical agreement in output value. The heat emission values
appear as square feet but are entirely empirical, being based on the heat
emission of the radiator and not on the measured surface.
Output of Wall Radiators
An^average value of 300 Btu per actual square foot of surface area per
hour has been found for wall radiators one section high placed with their
bars vertical. Several recent tests1 show that this value will be reduced
from 5 to 10 per cent if the radiator is placed near the ceiling with the bars
horizontal and in an air temperature exceeding 70 F. When radiators
are placed near the ceiling, there is usually so noticeable a difference in
temperature between the floor level and the ceiling that it becomes dif-
ficult to heat the living zone of a room satisfactorily.
^University of Illinois, Engineering Experiment Station Bulletin No. 223, p. 30.
264
CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS
Output of Pipe Coils
The heat emission of pipe coils placed vertically on a wall with the
pipes horizontal is given in Table 2. This has been developed from avail-
able data and does not represent definite results of tests. For such coils
the heat emission varies as the height of the coil. The heat emission of
each pipe of ceiling coils, placed horizontally, is about 12G Btu, 156 Btu,
and 175 Btu per linear foot of pipe, respectively, for l-in.t lj^-in., and
13/2-in. coils.
TABLE 2. HEAT EMISSION OF PIPE COILS PLACED VERTICALLY ON A WALL (PIPES
HORIZONTAL) CONTAINING STEAM AT 215 F AND SURROUNDED WITH AIR AT 70 F
Btu per linear foot of coil per hour (not linear feet of pipe)
SIZE OF PIPE
I
It?.
\\i IN.
VA IN.
Single row
132
162
185
±L s
Two
252
312
348
Four „ _
440
545
616
Six.
Eight. -
567
651
702
796
793
907
Ten -
Twelve
732
812
907
1005
1020
1135
Effect of Paint
The prime coat of paint on a radiator has little effect on the heat output,
but the finishing coat of paint does influence the radiation emission. Since
this is a surface effect, there is no noticeable change in the convection loss.
Thus, the larger the proportion of direct radiating surface, the greater
will be the effect of painting on the radiation. Available tests are on old-
style column type radiators which gave results shown in Table 3.
TABLE 3. EFFECT OF PAINTING 32-iN. THREE COLUMN, SIX-SECTION
CAST-IRON RADiATORa
RADIATOR
No.
FINISH
AREA
SQFT
COEFFICIENT
or HEAT TRANS.
BTU
RELATIVE
HEATING VALUE
PER CENT
1
2
3
4
Bare iron, foundry finish
One coat of aluminum bronze...
Gray paint dipped
27
27
27
27
1.77
1.60
1.78
1.76
100.5
90.8
101.1
100.0
One coat dull black Pecora paint —
^Comparative Tests of Radiator Finishes, by \V. H. Severns (A.S.H.V.E. TRANSACTIONS, Vol. 33,
1927, p. 41).
Effect of Superheated Steam
Available research data indicate that there is probably a decrease in
heat transfer rate for a radiator or gravity convector with superheated
steam in comparison with saturated steam at the same temperature.
The decrease is probably small for low temperatures of superheats and
additional tests are necessary with varying degrees of superheat to
establish accurate comparisons for all types of radiators and convectors2.
sTests of Radiators with Superheated Steam, by R. C. Carpenter (A.S.H.V.E. TRANSACTIONS, Vol. 7,
1901, p. 206).
265
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
HEATING EFFECT
For several years the heating effect of radiators has been considered by
engineers in order to use it for the rating of radiators and in the design of
heating systems. Heating effect is the useful output of a radiator, in the
comfort zone of a room, as related to the total input of the radiator3.
^CoW room temp m deg F
01234...
Net Ib of steam condensed per hour
5 52 Ib Test R-E2, 5-tube rad
5 62 Ib Test R-E61, 3-tube rad
5.42 Ib Test R-E10, 1-tube panel rad
— 5.50 Ib Test R-2c, (Bui 223) wall rad
5678
2 3
HEIGHT ABOVE FLOOR IN FEET
FIG. 1. ROOM TEMPERATURE GRADIENTS AND STEAM CONDENSING RATES FOR FOUR
TYPES OF CAST-IRON RADIATORS WITH A COMMON TEMPERATURE AT THE 60-lN. LEVEL
Note that the steam condensations are practically the same for all four radiators when the same air
temperature of 69 F is maintained at the 60-in. level. avr
6.68 Ib Test R-E56, 5-tube rad.
6.48 Ib Test R-E20, 3-tube rad.
6 12 Ib Test R-E58, 1-tube panel rad.
55.0 Ib Test R-2c, (Bui. 223} wall rad
7 8
HEIGHT ABOVE FLOOR IN FEET
FIG. 2. ROOM TEMPERATURE GRADIENTS AND STEAM CONDENSING RATES FOR FOUR
TYPES OF CAST-IRON RADIATORS WITH A COMMON TEMPERATURE AT THE 30-lN LEVEL
68 plsma^ai^d ^ SoSn^fel™ *" dftoBlt ^ aU *™ radiatOre when the sam< ** *»*«<**• of
The results of tests conducted at the University of Illinois are shown in
*igs. 1 and 24. For the four types of radiators shown, the following; con-
clusions are given:
« c °a»». by Dr- Charles Brabbee (A.S.H.V.E. TRANSACTIONS Vol 33 1927
266
CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS
1. The heating effect of a radiator cannot be judged solely by the amount of steam
condensed within the radiator.
2. Smaller floor-to-ceiling temperature differentials can be maintained with long, low,
thin, direct radiators, than is possible with high, direct radiators.
3. The larger portion of the floor-to-ceiling temperature differential in a room of
average ceiling height heated with direct radiators occurs between the floor and the
breathing level.
4. The comfort level (approximately 2 ft-6 in. above floor) is below the breathing line
level (approximately 5 ft-0 in. above floor), and temperatures taken at the breathing
line may not be indicative of the actual heating effect of a radiator in the room. The
comfort-indicating temperature should be taken below the breathing line level.
5. High column radiators placed at the sides of window openings do not produce as
comfortable heating effects as long, low, direct radiators placed beneath window
openings5.
HEATING UP THE RADIATOR AND CONVECTOR
The maximum condensation occurs in a heating unit when the steam
is first turned on6. Fig. 3 shows a typical curve for the condensation rate
in pounds per hour for the time elapsing after steam is turned into a cast-
iron radiator. The data are from tests on old style column type radiators.
;± i u
85
Qu
t 0.8
«
oe.
UJ
** OC
1
\
/
\
i
/
\
V
\
z
0
5n,
/
\l
/
\
RATE OF CONDENSE
o c
K) 4
/
\
\
/'
f
^v
/
10 20 30
TIME ELAPSED AFTER STEAM TURNED INTO RADIATOR, MINUTES
40
FIG. 3. CHART SHOWING THE STEAM DEMAND RATE FOR HEATING UP A CAST-IRON
RADIATOR WITH FREE AIR VENTING AND AMPLE STEAM SUPPLY
In practice the rate of steam supply to the heating unit while heating up
is frequently retarded by controlled elimination of air through air valves
or traps. Automatic control valves may also retard the supply of steam.
ENCLOSED RADIATORS
The general effect of an enclosure placed about a direct radiator is to
restrict the air flow, diminish the radiation and, when properly designed,
improve the heating effect. Recent investigations7 indicate that in the
design of the enclosure three things should be considered:
'Effect of Two Types of Cast-iron Steam Radiators in Room Heating, by A. C. Willard and M. K.
Fahnestock (.Heating, Piping and Air Conditioning, March, 1930, p. 185).
*The Cooling and Heating Rates of a Room with Different Types of Steam Radiators and Convectors,
by A. P. Kratz, M. K. Fahnestock and E. L. Broderick (A.S.H.V.E. JOURNAL SECTION, Heating, Piping
and Air Conditioning, April, 1937, p. 251).
'University of Illinois, Engineering Experiment Station Bulletin Nos. 192 and 223, and Investigation of
Heating Rooms with Direct Steam Radiators Equipped with Enclosures and Shields, by A. C. Willard,
A. P. Kratz, M. K. Fahnestock and S. Konzo (A.S.H.V.E. TRANSACTIONS, Vol. 35, 1929, p. 77).
267
HEATING VENTIIIATING AIR CONDITIONING GUIDE 1938
1. There should be better distribution of the heat below the breathing line level to
produce greater heating comfort and lowered ceiling temperatures.
2. The lessened steam consumption may not materially change the radiator heating
performance.
3. The enclosed radiator may inadequately heat the space.
A comparison between a bare or exposed radiator (A) and the same
radiator with a well-designed enclosure (j5), with a poorly-designed
enclosure (C), and with a cloth cover (D) will illustrate the relative
heating effects. In Fig. 4 the curve (B) reveals that the enclosed radiator
used less steam than the exposed radiator, but gave a satisfactory heating
performance. A well-designed shield placed over a radiator gives about
the same heating effect. Curve (C) shows the unsatisfactory effects
produced by improperly designed enclosures. Curve (D) shows that the
TEMPERATURE IN DEG FAHR
S S 3 S
^^
A-,
^
^j
_— —
'^
8
is'
^
^''
^
?
3t
•&'
^
<
^
XX
>-
Radiator
Steam consumption
Lb per hr
Per cent
V
/
A
B
C
D
5.44
4.71
4.50
4.59
100
86.6
82.7
84.4
2468
HEIGHT ABOVE FLOOR fN FEET
10
FIG. 4. STEAM CONSUMPTION OF EXPOSED AND CONCEALED RADIATORS
effect of a cloth cover extending downward 6 in. from the top of the
radiator was to make the performance unsatisfactory and inadequate.
Practically all commercial enclosures and shields for use on direct
radiators are equipped with water pans for the purpose of adding moisture
to the air in the room. Tests8 show that an average evaporative rate of
about 0.235 Ib per square foot of water surface per hour may be obtained
from such pans, when the radiator is steam hot and the relative humidity
in the room is between 25 and 40 per cent. This source of supply of
moisture alone is not adequate to maintain a relative humidity above
25 per cent on a zero day.
CONVECTORS OR CONCEALED HEATERS
Although any standard radiator may be concealed in a cabinet or
other enclosure so that the greater percentage of heat is conveyed to the
•University of Illinois, Engineering Experiment Station Bulletin No. 230, p. 20.
268
CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS
room by convection thereby resulting in a form of gravity con vector,
generally better results are obtained with specially designed units which
permit a free circulation of a larger volume of air at moderate tempera-
tures. Since air stratifies according to temperature, moderate delivery
temperatures at the outlet of the enclosure reduce the temperature dif-
ferential between the floor and ceiling and accordingly accomplish the
desired heating effect in the living zone.
Fig. 5 shows a typical built-in convectpr. The heating element con-
sisting of a large percentage of fin surface is usually shallow in depth and
SECTION
FIG. 5. TYPICAL CONCEALED CONVECTOR USING SPECIALLY DESIGNED HEATING UNIT
placed low in the enclosure in order to produce maximum chimney effect
in the enclosure. The air enters the enclosure near the floor line just
below the heating element, is moderately heated in passing through the
core and delivered to the room through an opening near the top of en-
closure. Since the air can only enter the enclosure at the floor line, the
cooler air in the room which always lies at this level, is constantly being
withdrawn and replaced by the warmer air. This air movement accom-
plishes the desired reduction in temperature differentials and assures
maximum comfort in the living zone.
The Convector Manufacturers Association has adopted the A.S.H.V.E.
Standard9 in the formulation of its ratings and has compiled a tentative
•A.S.H.V.E. Standard Code for Testing and Rating Concealed Gravity Type Radiation (Steam),
(A.S.H.V.E. TRANSACTIONS, Vol. 37. 1931. p. 367); (Hot Water). (A.S.H.V.E. TRANSACTIONS, Vol. 3<),
1933, p. 237).
269
HEATING VENTILATING AIR CONDITIONING GUIDE 1938
standard of heating effect allowances for various enclosure heights to be
included in the ratings by its members.
All published ratings bearing the title C.M.C. Ratings (Convector Manu-
facturers Certified Ratings) indicate that the convectors have been tested
in accordance with the A.S.H.V.E. Code by an impartial and disinterested
laboratory and that the ratings have been approved by the Standardiza-
tion Committee of the Convector Manufacturers Association.
Concealed heaters or cpnvectors are generally sold as completely
built-in units. The enclosing cabinet should be designed with suitable
air inlet and outlet grilles to give the heating element its best performance.
Tables of capacities are catalogued for various lengths, depths and heights,
and combinations are available in several styles for installations, such as
the wall-hung type, free-standing floor type, recess type set flush with wall
or offset, and the completely concealed type. Most of these types may be
arranged with a top outlet grille in a plane parallel with the floor, although
the front outlet is practically standard. In cases where enclosures are to
be used but are not furnished by the heater manufacturer, it is important
that the proportions of the cabinet and the grilles be so designed that they
will not impair the performance of the assembled convector. It is impor-
tant that the enclosure or housing for the convector fit as snugly as pos-
sible so that the air to be heated must pass through the convector and
cannot be by-passed in the enclosure.
The output of a convector, for any given length and depth, is a variable
of the height. Published ratings are generally given in terms of equiva-
lent square feet, corrected for heating effect. However, an extended
surface heating unit is entirely different structurally and physically from
a direct radiator and, since it has no area measurement corresponding to
the heating surface of a radiator, many engineers believe that the per-
formance of convectors should be stated in Btu's. For steam convectors,
as for radiators, 240 Btu per hour may be taken as an equivalent square
foot of radiation.
RADIATOR AND CONVECTOH SELECTION
Since the capacity of a radiator varies as the 1.3 power and a convector10
as the 1.5 power of the temperature difference between the inside of
radiator and surrounding air it is obvious that for other than 70 F room
temperatures the heat emission will be other than 240 Btu per square foot
of rating. Therefore in selecting the size of radiator or convector to be
used it is necessary to correct for this difference. Table 4 shows factors by
which radiation requirements, as determined by dividing heat load by
240, shall be multiplied to obtain proper radiator or convector sizes from
published rating tables for room temperatures ranging between 50 and
80 F as well as for steam or water temperatures from 150 to 300 F. For
other room and heating medium temperatures the factor is determined by
the following formulae:
For radiators:
Cs - /215 ~ 70V'3
"Factors Affecting the Heat Output of Convectors, by A. P. Kratz, M. K. Fahnestock, and E. L. Brod-
erick (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 443).
270
CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS
For con vectors:
where
Cs = correction factor.
/a — steam temperature, degrees Fahrenheit.
tT — room temperature, degrees Fahrenheit,
/i = average inlet air temperature, degrees Fahrenheit.
TABLE 4. CORRECTION FACTORS FOR DIRECT CAST-IRON RADIATORS AN*I>
Cox VECTOR HEATERS*
STEAM ., FACTORS FOR DIRECT „
PRESS. , bTEAM CAST-IRON RADIATOR FACTORS FOR ( UVVLIT JKS
AFFHOi. . YVxTEH ' R *P P ' T ,. 4 . ! T^..^^^..^. -^« t'
fiagp ' Ahh. TEMP.
Vacuum Lb p<-r ' F '
In. Hg ! Sqlri. j
80 , 75 70 65
60
55 , 50 80 75
70 , 65 GO
J3
5U
22A , 3.7 | 150
2.58 2.36 , 2.17 2.00
1.86
1.73 ] 1.62 ; 3.11 2.83
2.57 2.35
2.15
1.98
1.8*
20.3 4.7 ! 160
2.17
2.00 | 1.86
1.73
1.62
1.52 1.44 I! 2.57
2.35
2.15 1.98
1.84
1.71
1.59
17.7 , 6.0 j 170
1.86
1.73
1.62
1.52
1.44
L35 i 1.28 ;{ 2.15
1.98
1.84 i 1.71
1.59
1.49
1.40
14.6 7.5 . 180
1.62 ' 1.52 1.44
1.35
1.28
1.21 1.15 | 1.84
1.71
1.59 i 1.49
1.40
1.32
1.24
10.9 9.3 ! 190
1.44 1.35 , 1.28
1.21
1.15
1.10
1.05 i. 1.59
1.49
1.40 i 1.32
1.24
117
1.11
6.5 ! 11.5 | 200
1.28
1.21
1.15 ; 1.10
1.05
1.00
0.96 i 1.40
1.32
1.24 ; 1.17
1.11
1.05
1.00
LbperSqln.' I
• :i
!
1 • 15.6 i 215 1.10 ! 1.05 i 1 00
0.96
0.92 ' 0.88
O.S5 I- 1.17 1.11
1.05 i 1.00
095
0.91
087
6 '21 1 230 ! 0.96
0.92
0.88
0.85
0.81 0.78
0.76 j 1.00 0.95
0.91 | 0.87
0.83
0.79
0.76
15 , 30 250 j 0.81
0.78
0.76 0.73
0.70
0.68
0.66 'I 0.83
0.79
0.76 , 0.73 ; 0 70
0.68
005
27 : 42 i 270 0 70
068
0.66 0.64
0.62
0.60
0.58 ;| 0.70
0.68
0.65 I 0.63 j 0.60
0.58
0.56
52 i 67 ! 300 1 0.58
0.57
0.55
0.53
0.52
0.51
0.49:i 0.56 0.54
0.53 i 0.51 ! 0.49 j 0.4*
0.47
»To determine the heater size for a given space, divide the heat loss in Btu per hour by 240 and multiply
the result by the proper factor from the above table.
To determine the heating capacity of a heater at other than standard conditions, divide the heating
capacity at standard conditions by the proper factor from the above table.
CODE TEST FOR RADIATORS AND 
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11